The rules and specifications regarding golf clubs are divided into five separate categories, describing the requirements that apply to each. The five categories are:
By definition, the loft of a putter must not be greater than 10 degrees. Putters are permitted to have negative loft. However, a negative loft exceeding a magnitude of 15 degrees would not be considered “traditional and customary in form and make” (see Section 1a(i) below).
The Equipment Rules rarely distinguish between wood and iron clubs (see Section 4b, Dimensions, Volume and Moment of Inertia, for the main example of different treatment), but there are various instances throughout the Equipment Rules where certain specifications do not apply to putters or exceptions may be made for putters. These differences will be highlighted at the appropriate places throughout the Equipment Rules.
Probably as a consequence of these differences, confusion often exists as to which Equipment Rules apply to “chippers”. A “chipper” is an iron club designed primarily for use off the putting green, generally with a loft greater than ten degrees. As most players adopt a “putting stroke” when using a chipper, there can be a tendency to design the club as if it was a putter. To eliminate confusion, the Equipment Rules which apply to chippers include:
The club must be composed of a shaft and a head and it may also have material added to the shaft to enable the player to obtain a firm hold (see Section 3 below). All parts of the club must be fixed so that the club is one unit, and it must have no external attachments. Exceptions may be made for attachments that do not affect the performance of the club.
In explaining this provision, it is easier to break it down into the following 4 sections:
(i) Traditional and Customary Form and Make
The phrase “traditional and customary form and make” does not mean that clubs must look the same as they did 100 years ago. If so, for example, steel shafts and metal-headed woods would not conform.
The “traditional and customary” clause is used when there is not a specific provision that can be applied to a specific, non-traditional club feature, and/or the overall club design deviates from traditional appearance and/or construction standards. For clubheads, the “Plain in Shape” provision generally applies (see Section 4a, below).
(ii) Club Composition
This clause means that a club is not permitted to have multiple shafts or heads. It also highlights that it is not essential for a club to have material added to the shaft to form a grip. For further information on a club which has no material added to form a grip, see Section 3.
(iii) All Parts must be Fixed
This clause means that no part of the golf club should be designed to move, nor should it be promoted as doing so. Once assembled, all parts of the club which are bonded must be bonded such that they require heat to loosen (see Section 1b below for clubs which are designed to be adjustable). If any part of a club were to incorporate moving powder, pellets, liquid, vibrating wires, rollers, tuning forks, or any number of other features which could be considered a “moving part”, the club would not conform.
(iv) External Attachments
While this clause prohibits the attachment of anything to the club which could potentially have an effect on its performance (e.g. aiming bars or weights), other items may be permitted to be attached to certain parts of the club provided (a) no performance benefit can be derived, and (b) no other Equipment Rules are breached, as well as Rule 4.3 of the Rules of Golf (Use of Equipment).
Examples of attachments that could be permitted include:
Temporary, non-permanent attachments to the shaft such as decals for identification - such attachments, for identification only, may also be permitted on the clubhead (other than the face). Additionally, tape to protect the shaft is permitted. However, these attachments must not be usable for any other purpose (e.g. alignment).
The two long-standing permissible “external attachments” are (a) the permission to use lead tape on the shaft or the head for weighting, and (b) the use of a suction cup at the end of the grip of a putter to assist with retrieving the ball from the hole. While lead tape can affect the performance of the club and a rubber suction cup would exceed the diameter of the butt end of the grip, the use of both of these items continue to be permitted on a traditional basis (but see Section 4b(i) below for details on the use of lead tape on driver heads with a high Moment of Inertia).
All clubs may be designed to be adjustable for many different characteristics – for example, weight, length, lie and loft. In order to preserve the integrity of Rule 4.1a(3) of the Rules of Golf (“Deliberately” Changing Club’s Performance Characteristics During Round), the Equipment Rules clearly state that it must not be too easy for a player to make adjustments during a round and that the mechanism must be firmly fixed, with little chance of it working loose. All adjustment mechanisms must comply with the following requirements:
• Method of Adjustment
Adjustments must require the use of a special tool, such as an Allen key, a Phillips screwdriver or a custom made device. It must not be possible to make the adjustment just by using the fingers or some other object which would normally be kept in a golfer’s pocket, for example a coin or a pitch-mark repair tool.
• Unusable Unless Locked or Fully Tightened
If, as is often the case, a screw is used to fix the mechanism, the club must, for all practicable purposes, be unusable without the screw being in place and tightly fixed. One exception to this “unusable” requirement is for a long putter with a shaft which dismantles into two shorter lengths for travel purposes. Here, a screw together (“pool cue”) joint is permitted, in combination with an Allen key screw, or similar, which penetrates the threaded section of the joint by at least half way. The existence of both the threaded joint and the fixing screw potentially renders the putter usable, even when the screw is not tightened, or it is left out entirely. It also renders the putter potentially adjustable by hand. However, this exception was introduced as a specific concession for travel clubs.
• Friction Fit Mechanisms
Generally, friction fit adjustment mechanisms are not permitted because there is potential for them to be readily adjustable (i.e. the mechanism could be sufficiently tightened such that the club is usable, but not quite enough to prohibit it from being adjustable by hand). However, a friction fit mechanism which can be only locked and unlocked and is fixed in its locked state and unusable in its unlocked state, may be permitted upon evaluation.
• Discrete Steps
A mechanism that allows for an adjustment to be made in discrete steps may be permitted provided all other Equipment Rules and specifications are satisfied. Without the adjustment mechanism locked in place, the club must essentially be unusable.
The above restrictions have been included in the Equipment Rules in order to encourage the player to make all of the necessary adjustments to his or her clubs before starting the round, and to protect the player from either unwittingly or purposely making adjustments during a round.
When assessing the conformity of an adjustable club, it is important to remember the third condition listed in Part 2, Section 1b, and to check that it cannot be adjusted into a position which does not conform to the Equipment Rules. For example, a putter which is adjustable for lie must not be capable of being adjusted into a position where the shaft diverges from the vertical by less than 10 degrees (see Section 1d, below), or any other position which would render the club non-conforming (see Figure 1).
(ii) Adjustability for Weight
All clubs may be designed to be adjustable for weight, provided the adjustment mechanism conforms to the conditions described in Section 1b of the Equipment Rules. Examples of what would and would not be permitted are illustrated in Figure 2.
As noted in Section 1a, with respect to adjustments for weight, the only exception to the conditions described in Section 1b(i) above is the addition or removal of lead tape. This is a practice which pre-dates the introduction of the adjustability rules and is permitted on ‘traditional’ grounds. The addition, removal or alteration of lead tape during a round is not permitted (see Rule 4.1a(3) of the Rules of Golf).
(iii) Adjustability for Length
• All Clubs
All clubs may be adjustable for length, provided the adjustment mechanism conforms to the specifications already described and is consistent with other Equipment Rules.
Integrated mechanisms are permitted, provided the bending and twisting properties of the shaft remain substantially the same and the grip remains conforming. Mechanisms externally attached to the grip are not permitted.
Telescopic Mechanisms that can be fully extended into a locked position for use and collapsed for travel purposes may be permitted. However, the club must not be usable in its collapsed, unlocked state.
Non-integrated mechanisms attached to the shaft may be permitted for putters only, provided that:
(iv) Other Kinds of Adjustability
As previously noted, the adjustability provisions allow all clubs to be designed to be adjustable for many different characteristics – provided all specifications are satisfied. Manufacturers are encouraged, however, to submit all new adjustable design innovations for evaluation in the early stages of development.
The above provisions on club length mean that the concept of long and mid-length putters still conform to the Equipment Rules. However, The R&A and USGA have adopted a position that clubs designed for chipping, including modified wedges, that are longer than standard length clubs of similar loft are not traditional and customary in form and make (see Part 2, Section 1a).
The following table is used for the purpose of determining the maximum allowable length of a chipping club.
Loft Range (°)
Maximum Allowable Length (in)
Maximum Allowable Length (m)
When the club is in its normal address position the shaft must be so aligned that:
(i) the projection of the straight part of the shaft on to the vertical plane through the toe and heel must diverge from the vertical by at least 10 degrees (see Fig. 5). If the overall design of the club is such that the player can effectively use the club in a vertical or close-to-vertical position, the shaft may be required to diverge from the vertical in this plane by as much as 25 degrees;
(ii) the projection of the straight part of the shaft on to the vertical plane along the intended line of play must not diverge from the vertical by more than 20 degrees forwards or 10 degrees backwards (see Fig. 6).
For most putters, the “normal address position” is determined by the geometry of the head. The head would be placed on a horizontal flat surface, with the sole touching that surface at a point directly below the centre of the face. The shaft angle would then be measured with the head in this position (see Figure 8).
If the putter head shape or weight distribution is very asymmetric, it may be necessary to make a subjective judgement as to where the effective centre of the face is and then to sole the club directly below that point. The position of the head in this instance might not always be the position that was intended when the club was designed, but in some cases a judgement has to be made based on how the club could feasibly and effectively be used (see Figure 9).
The same subjectivity may also be needed when confronted with a putter which has a very curved sole (see Figure 10). As before, the conformance evaluation would take into account not only the manner in which the putter is designed to be used, but also the way it could feasibly and effectively be used, given the geometry of the head as well as other unique characteristics of the overall design. This interpretation is particularly relevant to long-shafted putters with very curved or multi-planed soles – but standard length putters of 34-38 inches can also be subjected to this assessment.
It should be noted that all putters can usually be positioned in such a way that the shaft diverges from the vertical by less than 10° or even to a position where the shaft itself is vertical. Also, it is unusual for the sole of a putter to be completely flat all the way from heel to toe. When faced with a ruling of this kind, the decision should not be based on whether a player uses the putter with the shaft in a position less than 10° – but whether the putter design facilitates this (see Figure 11).
If the overall design of a putter is such that a player can putt effectively with the shaft in a vertical or near-vertical position, it would be ruled contrary to Part 2, Section 1d, even if the shaft angle does satisfy the 10 degree Rule when the putter is in its “normal address position”. The shaft angle on such a putter would be required to be increased up to as much as 25 degrees. In assessing whether a putter can be used effectively in such a position and in order to determine what the shaft angle should be increased to, the combination of all of the following features must be considered:
This means that a long putter which has the shaft attached to the toe, a 10 degree lie angle in the toe to heel plane and a curved sole could potentially be ruled non-conforming. Even though each of these features, when taken in isolation, might conform to the Equipment Rules, it is the combination of these features which could lead to a non-conforming decision.
This is a good example of an area where rules officials should take care not to make decisions unless they are completely certain that it is correct. If, after examining the club and carrying out all of the appropriate consultations, it is still not possible to give a definitive ruling, a Duration of Competition or Duration of Round Answer should be given (see Supplementary Paper A – Advice to Rules Officials Concerning Queries on the Conformity of Clubs at Competitions).
The determination of a putter’s “normal address position” or whether it can be used in a vertical or close-to-vertical position can be highly subjective and in terms of those putters which are actually submitted to The R&A or USGA, the job of making rulings on them is only made easier because it is possible to compare them with previous submissions and rulings.
Except for putters, all of the heel portion of the club must lie within 0.625 inches (15.88 mm) of the plane containing the axis of the straight part of the shaft and the intended (horizontal) line of play (see Fig. 12).
The intent of the provision is to prevent centre shafted clubs (see Section 2c below – “Attachment to the Clubhead”), and the measurement of an iron club is illustrated in Figure 13.
It is worth highlighting that the heel portion of the club extends from the face all the way to the back of the head. Therefore, for unusually shaped heads (e.g. flared or square shaped), where the outermost part of the heel may be further back from the face than for more traditionally shaped heads, the measurement will be completed at that point.
It is also worth stressing that, in most cases, the shaft of a putter may be attached at any point on the clubhead (see Section 2c).
The shaft must be straight from the top of the grip to a point not more than 5 inches (127 mm) above the sole, measured from the point where the shaft ceases to be straight along the axis of the bent part of the shaft and the neck and/or socket (see Fig. 14).
This provision is interpreted to mean that the shaft must extend to the end of the grip, or at least that the grip should not extend beyond the top end of the shaft more than is necessary to accommodate the butt cap (see Figure 15).
The “5-inch” measurement should be made using a pair of callipers (to measure the depth of the head at the point where the shaft is attached) and a flexible measuring tape, or a piece of string (to measure the length of any bend or bends in the shaft from the point where the shaft ceases to be straight) (see Figure 16).
The point where the shaft ceases to be straight can be determined by placing a rigid steel ruler along the straight part of the shaft and marking the point where the shaft and the ruler are no longer in contact. This provision is particularly relevant to putters where the shaft is inserted directly into the head. (For putter heads that have a “neck” – see Section 2c).
It is challenging to assess the conformance of a shaft in the field. However, a standard shaft with a circular cross-section would most likely conform unless there is specific evidence to the contrary (e.g. claims by the manufacturer which indicate non-conformance, including advertising claims). A shaft which is not symmetrical in all axes (e.g. a shaft with an oval or rectangular cross-section) would not normally be expected to conform to the Equipment Rules. Manufacturers of shafts with unusual cross-sections or other unique features should submit them to The R&A or USGA for a ruling prior to marketing and/or manufacturing. Whether such a ruling exists can be confirmed by contacting The R&A or USGA.
Many graphite shafts have a small “spine” or “spines” running along the length of the shaft which may make them bend a little differently depending on how they are oriented during installation. The existence of a small spine is generally regarded as being the result of normal manufacturing processes and therefore not a breach of Section 2b. As previously noted, The R&A and USGA recognizes that it is difficult to produce a perfectly symmetrical shaft. Therefore, provided that the shaft is manufactured with the intention of meeting the above requirement, a reasonable tolerance is applied when evaluating shafts for conformance.
Manufacturers of clubs may orientate or align shafts which have spines for uniformity in assembling sets or in an effort to make the shafts perform as if they were perfectly symmetrical. However, a shaft which has been orientated for the purpose of influencing the performance of a club, e.g. to correct wayward shots, would be contrary to the intent of this provision.
The shaft must be attached to the clubhead at the heel either directly or through a single plain neck and/or socket. The length from the top of the neck and/ or socket to the sole of the club must not exceed 5 inches (127 mm), measured along the axis of, and following any bend in, the neck and/or socket (see Fig. 17).
Exception for Putters: The shaft or neck or socket of a putter may be fixed at any point in the head.
The most important points to remember here are that a club must only have one neck, that it must be “plain” and, in order to restrict elaborate shapes and curves, the length of the neck is limited to 5 inches (127 mm).
The interpretation of a “plain” neck is clarified as follows:
The neck must not be shaped for any purpose, other than connecting the shaft to the head in a traditional manner. While a neck may contain features such as an adjustability mechanism, a method for damping vibration or an alignment line, it must not be unusually shaped in order to house or accommodate such a feature. For example, in most cases, lines which have been painted or lightly engraved onto an otherwise plain neck are permitted. However, a neck designed specifically to accommodate such lines or marks would be considered non-conforming. Small scale features, on an otherwise plain neck, which are purely for decorative purposes, and could not effectively perform, or be used for, another purpose, may also be permitted.
The above requirements also apply to woods, however there is some accommodation for the transition area between the head of a wood and its neck. This transition area must fit within a cylinder of a diameter and height of 1 inch (25.4 mm) measured from the base of the transition and parallel to the axis of the shaft. Any transition which satisfies this restriction should be permitted provided it does not contain any other non-plain feature (for example, holes or alignment bars).
NOTE: Some exceptions may be made for clubheads made of wood. Ferrules shaped to circumvent this interpretation are not permitted.
The measurement of the length of a neck should be made in the same way as a bend in the bottom of a shaft (see Section 2a and Figure 16).
The majority of necks are designed to have the shaft inserted into them, and this normally avoids any confusion as to where the neck begins. However, if the neck is inserted into the shaft, the measurement should be taken from the end of the shaft.
Figure 18 contains diagrams of various neck features which would not be permitted.
The grip is primarily for the purpose of assisting the player in obtaining a firm hold – so that the club does not slip or twist out of the player’s hands. However, the installation of a grip onto the shaft is optional.
When no material is added to the part of the shaft designed to be held by the player, the provisions relating to the grip take precedence over the provisions relating to the shaft. Therefore, the dimensions and cross-section of that area of the shaft could change (per Section 3b) and equal bending in any direction would not be required (so Section 2b does not apply in this case).
In order to accommodate both hands, the grip must be at least 7 inches (177.8 mm) in length. This also applies to clubs which have been designed to be used one-handed. For putters which have two grips, see Section 3c below.
Due to the nature of grips and the grip provisions, it is sometimes challenging to make a ruling without examining and comparing examples of other grips which are known to either conform or not conform. However, this is not something which would normally be possible in the field. It may help to remember that the overall consideration is that a grip “must not be moulded for any part of the hands”. If a certain feature on the grip enables the player to place his or her hands in exactly the same position every time, solely by feel, then it must be determined whether that feature renders the grip “moulded for the hands”. An extreme example of a grip which would be ruled “moulded for the hands” is the type of training grip often used to help beginners. However, a grip which has subtle changes in surface texture would usually be considered conforming. Likewise, printed markings which assist with the correct placement of the hands visually would normally be considered conforming. Most of the details contained in Sections 3b and 3c below serve to clarify and expand on this basic principle.
To take these each in turn:
(i) Circular Cross-section for Woods and Irons
Grips on woods and iron clubs are allowed to deviate from circular by having a slightly raised rib running along the full length of the grip (often called a “reminder rib”).
“Slightly raised” is interpreted to mean that the maximum and minimum diameters of the cross-section at any point must not differ by more than 0.040 inches (1.016 mm). While this measurement can be taken using a pair of callipers, due to the nature of gripping materials, the results of these measurements should be interpreted with caution in the field. An additional requirement, mainly for the benefit of manufacturers, is that the dimension of the rib width, from edge to edge, should not exceed 50% of the grip’s internal diameter.
In the case of a standard length grip (approximately 10 inches (254 mm) in length), the “full length of the grip” is interpreted to mean that the rib must extend to within 3 inches (76.2 mm) of the tip (see Figure 20). This should generally be enough to cover the span of the player’s hands on the grip.
Simulated leather wrapped grips moulded out of a rubber-like material with an indented spiral or other similar indentations are considered to be circular in cross-section and are permitted, as long as the fingers cannot comfortably fit in between the spirals or indentations. Similarly, features such as lines, dots or other patterned indentations, which are too small to fit even the smallest of fingers, would not of themselves render a grip non-circular in cross-section. However, any feature which is considered wide and deep enough to accommodate a finger or fingers could be ruled “moulded for the hands” and, hence, non-conforming.
As clearly stated in this clause, a putter grip may have a non‑circular cross-section, provided that, among other things, the cross-section remains generally similar throughout the length of the grip.
In order to accommodate the popular (and somewhat traditional) “pistol-type” putter grips and also limit the amount of potential offset, the phrase “generally similar” is interpreted to mean: (i) that the butt (top) end of the grip must not involve a sharp change in slope or dramatic flare on the underside (see Figures 21(a) and (b)); (ii) that the flat front must extend to within 1 inch (25.4 mm) of the top and bottom ends (see Figure 21(c)); and (iii) if the axis of the grip and the shaft do not coincide, the grip must be at least 10 inches (254 mm) in length.
As with circular grips, features such as lines, dots, or other patterned indentations, which are too small to fit even the smallest of fingers, would not of themselves render a putter grip not “generally similar throughout the length of the grip” or “moulded for the hands”.
(iii) Cross-sectional Dimension
This clause is self explanatory, though it is important to note that the measurement may be made in any direction on the horizontal plane, including diagonally.
(iv) Axis of the Grip
This clause requires that the axis of the circular grip on an iron or wood club coincides with the axis of the shaft. Therefore, a circular grip with the maximum diameter of 1.75 inches (44.45 mm) must not be mounted onto the shaft either off-centre or at an angle.
Where a putter has two grips, these grips are only considered separate if the gap between them is at least 1.5 inches (38.1 mm) in length. If a smaller gap exists, or if no gap exists, the total length from the bottom of the lower grip to the top of the upper one would be considered “one grip”. Therefore, it is unlikely that the grip would conform if two conventional circular grips were installed without the required gap. Either the exposed piece of shaft between the two grips would constitute a waist, or the point where the two grips meet in the middle would cause a bulge. If there was no gap between the upper and lower grip, the grip could conform if the lower grip is a continuation of the upper grip, i.e. a continuation of the same taper, and the transition between the two sections is smooth (see Figure 22(d)).
If a putter does have two separated grips, the upper grip must be at least 5 inches (127 mm) in length. If the grip does not satisfy this requirement, it would be considered to be “moulded for the hands”.
Note: It is worth emphasising that it is not permissible for wood or iron clubs to have more than one grip.
The essence of Section 4a is encapsulated in the first three sentences of the general provision:
The clubhead must be generally plain in shape. All parts must be rigid, structural in nature and functional. The clubhead or its parts must not be designed to resemble any other object.
This provision basically means that the design of the clubhead must be free from gimmicks (though putters are viewed more liberally than woods and irons), must have the general appearance of a golf clubhead as opposed to another object and must not incorporate features which are designed to resemble another object (see Figure 23). All parts of the head (including permanent, permissible appendages) must be rigid throughout their length. As a general guideline, “rigid” means that it must not be possible to bend or flex the head or its parts by hand (see Figure 24).
It is not practicable to define plain in shape precisely and comprehensively. However, features that are deemed to be in breach of this requirement and are therefore not permitted include, but are not limited to:
The above statement acknowledges that defining whether a clubhead is “plain in shape” is subjective. To better clarify the provision and its interpretation, it is split into two categories – one which covers “all clubs” and the other which covers the additional specifications relevant only to “irons and woods” The Section also reflects the more liberalized application for putters which has evolved over the years and provides more detail regarding what is and what is not permitted for iron heads and woodheads. Following are general guidelines and illustrations for the two categories of “plain in shape”:
(i) All Clubs
• holes through the face;
• holes through the head (some exceptions may be made for putters and cavity back irons);
• features that are for the purpose of meeting dimensional specifications;
• features that extend into or ahead of the face;
• features that extend significantly above the top line of the head;
• furrows in or runners on the head that extend into the face (some exceptions may be made for putters); and
• optical or electronic devices.
To take each of these clauses in turn:
Holes through the Face
Holes through the face are not permitted – see Figure 25.
Holes through the Head
Features for the purpose of meeting Dimensional Specifications
For all clubs, the distance from the heel to the toe of the clubhead must be greater than the distance from the front to the back (see Section 4b, below). Clubs which incorporate features which are designed to or have the effect of circumventing this requirement are not permitted – see Figure 29.
Features above the top line of the head
Furrows and Runners
The application of this provision is fairly straightforward in most cases and can be determined simply by placing a straight edge along the leading edge of the face and looking to see if there is a gap between these two edges. However, woods and hybrids commonly have a smooth transition between the face and the rest of the body which can sometimes make it difficult to determine, in a repeatable and reproducible manner, whether features “extend into” or intersect the face.
Where the transition between the body and the face is not clearly defined, i.e. the face does not meet the body at a sharp edge or chamfer, the point of intersection shall be defined as the point where a line inclined at 45° from the reference plane is tangent to the cross-section (see Figure 35).
Projecting the points of intersection so defined onto the reference plane may be used to define a profile (see Figure 36).
Any substantial concavities in said profile are considered sufficient evidence that a runner or furrow extends into the face and thus does not conform with Section 4a(i).
Where the transition between the body and face is clearly defined by a chamfer of at least 45° with respect to the face, furrows and/or runners are permitted to intersect the chamfered surface, provided the feature does not intersect the face itself (see Figure 37).
Clubheads which incorporate prisms, mirrors, reflective materials, light beams, metronomes or mechanical devices such as spirit levels are not permitted – see Figures 39 and 40.
(a) the club’s owner, such as address and phone number;
(b) inventory tracking information;
(c) detection of the club’s use during a round.
Any such device must meet all other requirements of the Equipment Rules and must not vibrate or emit light or sound. If the device is capable of any function other than identification, the golf club will be considered not traditional and customary in form and make (see Section 1a (i)) and, therefore, non-conforming.
Note: Any device or application used in conjunction with a club incorporating such a device must comply with the provisions of Rule 4.3 of the Rules of Golf.
In addition to the provisions above, the “plain in shape” guidelines and illustrations for woods and irons are:
(ii) Woods and Irons
Cavities in the Outline of the Heel and/or Toe
When making this assessment, “viewed from above” is interpreted to mean the range from directly above the head to the normal address position for that club. The restriction does not apply to horizontal cavities around the skirt of the head, which might be visible from above – see Figures 41a and b.
Severe or Multiple Cavities in the Outline of the Back of the Head
Features Extending Beyond the Outline of the Head
Any fin, knob, appendage or plate which is protruding beyond the outline of the head is not permitted, whatever the purpose.
NOTE: While this provision does not apply to putters, The R&A and USGA have determined that unusual features which protrude beyond the outline of the toe and/or heel of a putter head may be ruled not “plain in shape” or not “traditional and customary”. However, as previously noted, other permanent appendages to the putter head are permitted provided that:
Section 4b is divided into three categories – woods, irons and putters. The volume and moment of inertia limits apply only to woodheads.
The volume of the clubhead must not exceed 460 cubic centimetres (28.06 cubic inches), plus a tolerance of 10 cubic centimetres (0.61 cubic inches).
In practice, many of the larger headed clubheads in the market place have a marking somewhere on the head indicating the approximate volume of the head (this is the cubic centimetres or “cc” value).
Fortunately, for clubs where there is no indication of volume, there is a fairly simple method of determining the actual volume of a clubhead in the field and it is broadly based on Archimedes’ Principle and the displacement of water. All that is needed is a large measuring container, half filled with water. The measure of clubhead volume would be the amount by which the water level rises once the clubhead has been submerged into the water. Therefore, if the container is filled with 1 litre of water and the level rises to 1450 millilitres when the head is submerged to the base of the hosel – this would mean that the head has a volume of 450 cubic centimetres.
The official test protocol for measuring volume is a more accurate method, but not that much more complicated, and it requires a similar container of water placed on a set of digital weighing scales.
Archimedes’ Principle states that the buoyant force on a submerged object is equal to the weight of the fluid that is displaced by the object – and since water has a specific gravity of 1.0, this means that 1 cubic centimetre of water has a mass of 1 gram. Therefore, the container of water should be placed on the scales and the weight should be set to zero. When the head is submerged in the water, the weight displayed on the scales (in grams) is equivalent to the volume of the head (in cubic centimetres).
In situations where a club is marked with a “cc” value which is in excess of the Rule (i.e. above 460 cubic centimetres), The R&A’s and USGA’s policy is to rule that the club is non-conforming – regardless of the actual volume measurement. This is to avoid confusion in the marketplace.
Prior to measuring the volume of a clubhead, the head should be inspected for cavities. All cavities on the crown should be filled with waterproof clay or other similar material to create a ‘straight line’ which connects the edges of the cavity. The ‘straight line filling technique’ does not follow the taper or curvature of the surface of the head, rather the cavity is filled so that it becomes a flat surface which adjoins the outer edges.
Only significant concavities on the sole will be filled, meaning any cavity or series of cavities which have a collective volume of greater than 15 cc.
When the club is in a 60 degree lie angle, the moment of inertia component around the vertical axis through the clubhead’s centre of gravity must not exceed 5900 g cm2 (32.259 oz in2), plus a test tolerance of 100 g cm2 (0.547 oz in2).
The MOI test is a measurement of a clubhead’s resistance to twisting and, therefore, it is an indication of its ‘forgiveness’.
The measurement of MOI is one of the few limits within the Equipment Rules which cannot easily be performed in the field. This is because the testing equipment is very specialized and it can only be measured by de-shafting the head (the hosel remains on the head for the purpose of the test). However, high MOI is only associated with modern, hollow, high volume driver heads and, due to the publication of the List of Conforming Driver Heads (see Rule 4c below), most of these clubs are now routinely submitted to the Governing Bodies for a ruling – so that they can be included on this List.
As the MOI of a driver head is affected by a change in its weight and the position of the centre of gravity, a driver which is designed to be adjustable for weight must conform to the Equipment Rules in all configurations (see Rule 1b). Moreover, when adding additional weight to a driver (e.g. with lead tape), the player must be certain that the club is still within the limit. To assist golfers with this determination, The R&A and USGA have developed a policy whereby if a driver head is submitted for a ruling and it is measured to have an MOI which is close to the limit, the manufacturer will be encouraged to advise its customers that the addition of any other weights to that model (including lead tape), other than the weights which were supplied by the manufacturer, is not permitted as it would likely render the club non-conforming. Additionally, the manufacturer must take care over its claims and must not advertise that the product is over the limit for MOI.
When the clubhead is in its normal address position, the dimensions of the head must be such that the distance from the heel to the toe is greater than the distance from the face to the back.
In practice, due to the shape and size of iron heads, this provision is rarely encroached. It is retained in the Equipment Rules, in part, to help maintain the traditional shape by which irons are recognized. However, while most irons are still relatively narrow from front to back, the popularity of hybrid clubs means that this provision has greater utility today.
(iii) Putters (see Fig. 44)
For traditionally shaped heads, these dimensions will be measured on horizontal lines between vertical projections of the outermost points of:
• the heel and the toe of the head;
• the heel and the toe of the face; and
• the face and the back;
and on vertical lines between the horizontal projections of the outermost points of the sole and the top of the head.
For unusually shaped heads, the toe to heel dimension may be made at the face.
Given all of the dimensional restrictions for putter heads, which help define the size and shape, the additional clause regarding unusually shaped heads is rarely, if ever, applied.
It is important to note that appendages are not permitted if their only purpose is to make the clubhead meet the dimensional specifications described in this provision (see Section 4a(iv) and Figure 29).
Given that the “spring-effect rule” is purely a performance related limit which cannot be measured easily in the field without specialized equipment and cannot be assessed through a visual inspection of the clubhead, The R&A and USGA have compiled and maintain a List of Conforming Driver Heads. This List can be accessed via The R&A’s or USGA’s website and it is updated weekly.
For competitions involving highly skilled players, a Term of Competition may be introduced requiring players to use a driver which is included on this List. This Term is an additional requirement for these players, which means that, not only must their clubs conform to the Equipment Rules, but the model and loft must also be included on the List of Conforming Driver Heads. This Term is not recommended for use at other levels of golf. However, it is the player’s responsibility to ensure that his or her driver conforms to the Equipment Rules if it is not on the List.
As well as meeting the requirements of clause (i) in the above Rule, clubs are also tested for compliance to clause (ii) using the Pendulum at points on the face other than at the centre and, depending on the results, other tests may be carried out. Any club which is found to include a feature that is designed to act like a spring, independent of the level of flexibility achieved by the design, could be ruled non-conforming.
Finally, if claims of “spring like” qualities are made by the manufacturer which suggest that a club is manufactured to be in excess of the limit, or there is evidence to suggest that the club is indeed over the limit, then the club would be deemed to be non-conforming.
The clubhead must have only one striking face, except that a putter may have two such faces if their characteristics are the same, and they are opposite each other.
The exception for putters was introduced in order to accommodate traditional blade Determining whether a surface constitutes a second (or third) striking face is often a matter of interpretation. However, in general, a surface should be considered an additional striking face if:
All three of the putters illustrated in Figure 45 would be ruled non‑conforming.
The face of the club must be hard and rigid and must not impart significantly more or less spin to the ball than a standard steel face (some exceptions may be made for putters). Except for such markings listed below, the club face must be smooth and must not have any degree of concavity.
If claims of excessive spin are made by the manufacturer, or if there is strong supporting evidence of excessive spin, then the club would be deemed to be non-conforming.
The “hardness” provision is particularly relevant to putters, many of which have a urethane or other “soft” material inset in the face.
The measure for hardness is made using a durometer. A putter face must be no less than 85 on a Shore A scale durometer. A simple measure of hardness in the field would be to use a fingernail. If a fingernail leaves a significant imprint in the face of a club, it is possible that the material does not satisfy the “hard and rigid” requirement. The face of a wood or iron club must be substantially harder than a putter face, i.e. no less than 75 on the Shore D scale.
In the field, “rigidity” is interpreted to mean that the face should not have any visible signs of movement or flex when manual pressure is exerted.
Where there is an inset in the face of the club, it should be flush with the rest of the face so that the face can still be considered smooth with no concavity. While we interpret concavity in this provision strictly, we also recognize that, due to manufacturing tolerances, it is sometimes difficult for every insert to be exactly flush with the rest of the face. As a result, we allow an inset to be up to 0.006 inches (0.15 mm) proud of the rest of the face or no deeper than 0.004 inches (0.1 mm) below the rest of the face.
(i) Definition of “Impact Area”
For iron clubs, the “impact area” is deemed to be that part of the club face where a treatment has been applied (for instance grooves, sandblasting, etc.) or the central strip down the middle of the club face having a width of 1.68 inches (42.67 mm), whichever is greater.
The impact area on driving clubs and fairway woods is deemed to be the central strip down the middle of the clubface having a width of 1.68 inches (42.67 mm) – see Figure 47a.
For clubs with insets in the face, the boundary of the impact area is defined by the boundary of the inset, as long as any markings outside the boundary do not encroach the impact area by more than 0.25 inches (6.35 mm) and/or are not designed to influence the movement of the ball.
Moreover, the inset itself must extend to at least 0.84 inches (21.34 mm) either side of the centre line of the face and to within at least 0.2 inches (5.08 mm) of the top line and leading edge of the face.
The above definitions of the impact area only apply to models of clubs manufactured on or after 1 January 2010. For clubs manufactured prior to 1 January 2010, please refer to the end of Supplementary Paper B.
(ii) Impact Area Roughness
When dealing with the surface roughness of a club face (not including putters, see Section 5f), the claims made by the manufacturer must be taken into account – especially if there is a claim that the roughness of the face influences the movement of the ball. In the absence of such claims, the ruling is made purely on the amount of roughness there is. Sandblasting or other treatments of roughness greater than 180 micro inches (4.5 µmetre) are not permitted. In addition to this requirement for roughness, milling is not permitted if the crest to trough depth exceeds 0.001 inches (0.025 mm). A reasonable tolerance is allowed for both of the above measurements. Non-conforming sandblasting or milling usually feels rough to the touch.
(iii) Impact Area Material
The requirement that the whole of the impact area must be of the same material does not apply to clubs made of wood or putters (see Section 5f). The reason why it does not apply to wooden headed clubs is to allow the continued use of traditional wooden clubs which have plastic insets and brass screws in the centre of the face. This design was commonly used in the old persimmon woods, some of which may still be in use. It is worth noting that a club face or inset made of a composite material would be considered to be of a single material and, therefore, would not be contrary to this provision.
Metal wood club faces which have insets of different material not trapezoidal in shape may be permitted if the height of the inset meets the definition of the impact area and the width of the inset is the same as the height in at least one point. However, in order to preserve the intent of the “same material” Rule, clubs which have unusually shaped insets of different material (i.e. other than circular, oval, square or rectangular) would not normally be permitted.
If an inset of different material is permitted under the above guideline, the inset would be considered the impact area for that club. Therefore, any markings outside that area need not conform to the specifications in Section 5c. However, such markings must not be designed to unduly influence the movement of the ball.
If a club has grooves and/or punch marks in the impact area they must meet the following specifications:
• Grooves must be straight and parallel.
• Grooves must have a symmetrical cross-section and have sides which do not converge (see Fig. 48).
• Grooves must not have sharp edges or raised lips.
• *For clubs that have a loft angle greater than or equal to 25 degrees, groove edges must be substantially in the form of a round having an effective radius which is not less than 0.010 inches (0.254 mm) when measured as shown in Fig. 50, and not greater than 0.020 inches (0.508 mm). Deviations in effective radius within 0.001 inches (0.0254 mm) are permissible.
(ii) Punch Marks
• The maximum dimension of any punch mark must not exceed 0.075 inches (1.905 mm).
• The distance between adjacent punch marks (or between punch marks and grooves) must not be less than 0.168 inches (4.27 mm), measured from centre to centre.
• The depth of any punch mark must not exceed 0.040 inches (1.02 mm).
• Punch marks must not have sharp edges or raised lips.
• *For clubs that have a loft angle greater than or equal to 25 degrees, punch mark edges must be substantially in the form of a round having an effective radius which is not less than 0.010 inches (0.254 mm) when measured as shown in Figure 50, and not greater than 0.020 inches (0.508 mm). Deviations in effective radius within 0.001 inches (0.0254 mm) are permissible.
Note 1: The groove and punch mark specifications above indicated by an asterisk (*) apply only to new models of clubs manufactured on or after 1 January 2010 and any club where the face markings have been purposely altered, for example, by re-grooving. For further information on the status of clubs available before 1 January 2010, refer to the ‘‘Equipment Search’’ section of www.randa.org or “Club and Ball Lists” section of www.usga.org.
Note 2: The Committee may require, in the Terms of Competition, that the clubs the player carries must conform to the groove and punch mark specifications above indicated by an asterisk (*). This Term is recommended only for competitions involving expert players. For further information, refer to to the Commitee Procedures, Section 8, Model Local Rule G-2 in The Official Guide to the Rules of Golf.
The groove and punch mark specifications were updated in 2010 and many pre-2010 models of clubs do not meet the new specifications. The above Notes mean that the vast majority of golfers can continue to carry clubs manufactured prior to 2010 until at least 2024.
Supplementary Paper B sets out guidance on how to measure width, depth and separation of grooves using the ‘ink and scratch’ method and how to determine the conformance status of a club to the pre-2010 Equipment Rules. This is an adequate method for use in the field where the Committee has not introduced the Groove and Punch Mark Term of Competition (i.e. at the non-elite level).
There are several methods which can be used to measure grooves and punch marks against the updated specifications detailed above – most of which require specialized equipment.
Full details of the procedure for measuring club face markings and determining their status against the post-2010 specifications can be found on The R&A’s and USGA’s websites. A summary can also be found in Supplementary Paper C.As noted, The R&A and USGA do not recommend adoption of the Term of Competition referenced in Note 2 unless the competition involves professional-level players and/or players at the highest levels of amateur golf. In order to assist players and officials to determine whether a player’s clubs meet the condition, The R&A and USGA have compiled an informational database of irons, wedges, fairway woods and hybrids that have been submitted to either organization and evaluated for conformance to the updated specifications. This information is available on The R&A’s and USGA’s websites, respectively.
Notably, clubs where the face markings have been purposely altered, for example, by re-grooving must conform to the 2010 groove and punch mark specifications. However, clubs which have only been refurbished back to their original state (perhaps by light sandblasting) may still benefit from the of grace given to pre-2010 models.
For the avoidance of doubt, all new models available after 31 December 2009 must conform to the current Equipment Rules.
(iii) Groove/Punch Mark Combinations
If punch marks are used in conjunction with grooves, the following guidelines apply:
Metal Wood Clubs
Provided the following three conditions are satisfied, the above interpretation of the specifications for punch marks in line with a groove may also be granted for metal woods, even if the punch marks would not be totally contained by the continuation of the groove:
Fig. 53 illustrates each of the above conditions:
The centre of the impact area may be indicated by a design within the boundary of a square whose sides are 0.375 inches (9.53 mm) in length. Such a design must not unduly influence the movement of the ball. Decorative markings are permitted outside the impact area.
This provision permits small, decorative logos in the centre of the face or at the side of the impact area (see Fig. 54). Decorative markings or logos that marginally encroach on the impact area, i.e. by less than 0.25 inches (6.35 mm), may be permitted. However, any such markings must not be designed to unduly influence or have the effect of unduly influencing the movement of the ball. Markings outside the impact area which are designed to influence the movement of the ball when it has been mis-hit would be contrary to this provision.
Any markings on the face of a putter must not have sharp edges or raised lips. The specifications with regard to roughness, material and markings in the impact area do not apply.
In addition, if a groove or the grooves on the face of a putter exceed 0.035 inches (0.9 mm) in width and 0.020 inches (0.508 mm) in depth, the following guidelines apply: