The R&A - Working for Golf
Conformance of Balls
The Equipment Rules
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4
Conformance of Balls

The Rules and specifications regarding the golf ball are divided into the following six categories:

  1. General
  2. Weight
  3. Size
  4. Spherical Symmetry
  5. Initial Velocity
  6. Overall Distance Standard.
4.1
General

The ball must not be substantially different from the traditional and customary form and make.  The material and construction of the ball must not be contrary to the purpose and intent of the Rules.
Prior to 2008, all of the provisions on the golf ball were precise and quantitative in comparison to the generally more descriptive Equipment Rules that relate to clubs. However, in 2008, new language was introduced to protect against any new technology which may be developed in the future which circumvents the intent of the existing Equipment Rules. Therefore, along with the guidelines and specifications listed below, The R&A or USGA may conduct additional testing and inspections to identify whether golf balls contain unusual material, construction and/or performance characteristics which might be considered substantially different from the traditional and customary form and make and/or contrary to the purpose and intent of the Equipment Rules.

 

Golf Ball Construction

 

Only golf balls constructed entirely from elastomeric materials (i.e., viscoelastic materials having a low elastic modulus) will be considered to be of traditional and customary form and make. Allowance may be made for the presence of some traces of non-elastomeric materials. The elastomeric materials may be thermoset or thermoplastic polymers, but must not be designed or manufactured to facilitate intentional modification of the ball’s playing characteristics. In addition, the design of the golf ball may not include parts or components that move with respect to each other or the ball or that are not concentric with the golf ball. Exceptions to the requirement that the ball must not be substantially different from the traditional and customary form and make are noted below.

 

Exceptions:

Golf balls may have a single, concentric core with a diameter of ≤ 0.9-in (22.9mm), provided that the core:  

  • contains fluid constrained within a single chamber; OR
  • if non-elastomeric, is effectively rigid (such as a solid or hollow, thick shell metallic sphere).
An embedded computer chip may be permitted within the ball for identification purposes, provided that the ball meets all other conformance requirements.
4.2
Weight
The weight of the ball must not be greater than 1.620 ounces avoirdupois (45.93 g).
This is one of the simpler tests, as all that is required is an accurate set of scales.  There is no minimum weight thus a ball can be as light as the manufacturer desires.
4.3
Size
The diameter of the ball must not be less than 1.680 inches (42.67 mm).
The official test protocol uses a metal ring gauge suspended in perspex.  It is important to note that there is no maximum size, the ball can be as large as desired provided it conforms to all other standards.
4.4
Spherical Symmetry
The ball must not be designed, manufactured or intentionally modified to have properties which differ from those of a spherically symmetrical ball.
The intent of this provision is simply to ensure that a ball is manufactured and designed to behave symmetrically.
4.5
Initial Velocity
The initial velocity of the ball must not exceed the limit specified under the conditions set forth in the Initial Velocity Standard for golf balls on file with The R&A and USGA.
There is a formal test procedure carried out using equipment approved by The R&A and USGA to evaluate whether golf balls meet the Initial Velocity specification.  The intent of the provision is to limit the speed of the ball off the clubface.  Full details of the test specification are available on The R&A’s or USGA’s website.
4.6
Overall Distance Standard
The combined carry and roll of the ball, when tested on apparatus approved by The R&A and USGA, must not exceed the distance specified under the conditions set forth in the Overall Distance Standard for golf balls on file with the R&A and USGA.
This provision was first introduced in 1976 in order to restrict the overall distance (carry and roll) a ball can travel under certain specific conditions.  This test protocol is continuously reviewed to ensure that it reflects the modern game and modern equipment.