For many golfers (us included), finishing a round with the same golf ball you started with is a real source of pride. It might look like it was chewed on by a goat for a few hours, but hey, if you don’t lose it, at least you can say you kept it in play all afternoon.
For those, however, who can’t help but lose a ball or three during a round (us included), a natural question emerges: If you start playing your round with one type of golf ball, do you have to keep playing the same type of ball the rest of the round? For example, if you played a Titleist ProV1 on the first hole, do you have to commit to that brand—and that model—until you hole out on 18?
There is an option in the Rules of Golf for a course/committee to employ something known as the “one-ball rule.” Technically, this is Model Local Rule that can be put in effect—almost always only in competitions—that says you must play with the same brand, make and model of ball you started the round with. This means that if you start playing with a Srixon Z-Star, you must play that type of ball for the remainder of the round and may not switch to another brand or even another model of Srixon. For reference, see “Committee Procedures; Model Local Rule G-4.” The penalty for somebody who mistakenly plays a different ball is two shots for each stroke made with the incorrect ball.