The Rules and specifications regarding the golf ball are divided into the following six categories:
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.
Golf balls may have a single, concentric core with a diameter of ≤ 0.9-in (22.9mm), provided that the core: