Q. What is the one ball rule?
A. The one ball rule is an optional condition that Committees may choose to use. If this rule is in effect, you must play with the same brand, make and model of golf ball that you started the round with. This means that if you start playing with a Titleist Pro V1, you must play a Titleist Pro V1 for the remainder of the round and may not switch to another brand or even another model of Titleist golf ball (see Committee Procedures; Model Local Rule G-4).