The next time you compete in a tournament you might want to check whether a One-Ball local golf rule is in place as to avoid receiving costly penalty strokes in your round.
The ruling only typically comes into play at Tour events and high-level amateur events, but some committees have been known to introduce this one now and again.
Should Model Local Rule G-4 ever be called into play by your tournament committee, then it will mean you can only play with the exact same brand, make and model of golf ball all the way through the round.
It can be a different number, though.
If you switch to play a different golf ball during the round then you will receive a two-stroke penalty for every stroke made with that golf ball.
You can of course change your golf ball in between holes, but you must make sure it's the exact same make and model of golf ball in this instance.
Players can change golf balls if the ball is cracked at any stage, but they cannot switch balls if it's just deemed to be scratched.
If Model Local Rule G-4 is not deployed, which is more often than not the case at amateur level, then you can play any golf ball you wish during the round.
Here's all you need to know about Model Local Rule G-4 should your tournament committee ever put it in play, according to the USGA:
Model Local Rule G-4: One Ball Rule
Purpose: To prevent a player from using balls with different playing characteristics depending on the nature of the hole or shot to be played during a round, the Committee can choose to require that a player use only a single type of ball that is on the List of Conforming Golf Balls.
Each individual listing on the List of Conforming Golf Balls is considered a different ball. Golf balls of different colours with identical markings are considered different balls.
This Local Rule is recommended for use only in competitions limited to highly skilled players (that is, professional competitions and elite amateur competitions).
Model Local Rule G-4
During an entire round, each ball at which the player makes a stroke must be the same brand and model as found in a single entry on the current List of Conforming Balls.
If a different brand and/or model is dropped, replaced or placed but has not yet been played, the player may correct the mistake by stopping use of that ball, without penalty, under Rule 14.5. The player must drop, replace or place a ball of the same brand and model as used at the start of the round.
When the player discovers he or she has played a ball in breach of this Local Rule, he or she must stop using that ball before playing from the next teeing area and complete the round with a ball of the same brand and model as used at the start of the round; otherwise the player is disqualified.
If the discovery is made during the play of a hole, the player may complete play of this hole with the ball played in breach or place a ball of the correct brand and model on the spot where the ball played in breach of this Local Rule was lifted from.
Penalty for Making a Stroke at a Ball in Breach of Local Rule
The player gets the general penalty for each hole during which he or she is in breach of this Local Rule.