The "One Ball" Condition
The Committee may introduce a condition of competition stating that a player must use balls of the same brand and type, and accordingly, a player may not change the brand name and cannot change from a brand type to another type of the same brand. Again, this condition is recommended for elite events only. The R&A does not currently introduce this condition at any of its Amateur events, but it is introduced at The Open Championship. The suggested wording for such a condition is contained in Appendix I, Part C of the Rules of Golf.