Golf ball manufacturers may submit golf balls to The R&A for conformance testing and subsequent inclusion on the List of Conforming Golf Balls.
Full details of the golf ball submissions procedure (including testing fees) and the golf ball specification sheet can be downloaded from this page.
List of Conforming Golf Balls
In the note to Rule 4.2a, it states that "The Committee may require, in the conditions of a competition (MLR G-3), that the ball the player uses must be named on the current List of Conforming Golf Balls issued by The R&A".
This List includes all those balls which have been submitted by manufacturers for testing, and which have been found to conform to the specifications laid down in Appendix III of the Rules of Golf.
It is recommended that the List is used for competitions involving expert players (ie Professional and top Amateur events). Use of the List in other events and Club golf is not recommended, but it is at the discretion of the Committee.
A Committee wishing to implement the 'Conforming Golf Ball Condition' should refer to the Rules of Golf, MLR G-3.
The full List can be downloaded from this page or searched using the link provided.