22/01/2026
Bowling Association Members,
For any USBC sanctioned competition or league, according to the USBC Playing Rules Chapter 8, Equipment Specifications, the rules are clear on drilled holes:
RULE 7. Drilling Requirements. All balls used in USBC certified competition must meet the following requirements:
1) Holes.
a) Holes or indentations for gripping purposes
i) Shall not exceed five and shall be limited to one for each finger and one for the thumb, all for the same hand.
ii) Shall not exceed 1-9/16” diameter and 4-1/2” deep, including holes required to install removeable devices.
iii) Must be used on every delivery.
b) Any secondary hole drilled inside of a gripping hole that is not intended for gripping purpose is considered a void
and not allowed.
c) No balance holes are allowed.
d) Balls without a thumbhole must have a scribed or engraved cross-hair lines (“+”) near the center of the palm to
indicate the grip orientation. The ball must be delivered in the marked orientation (i.e. palm must cover the “+”).
e) One vent hole for each finger and/or thumb hole, not to exceed 1/4 inch in diameter is permitted.
f) One mill hole for inspection purposes not to exceed 5 ⁄8 inch in diameter and 1⁄8 inch in depth is permitted."
This goes for every bowler, but in addendum, two-handed or no-thumb bowlers who don’t use the thumb during a delivery cannot have a thumb or a balance hole. If the ball does, it is illegal and games are subject to forfeiture. All holes drilled must be used for gripping purposes on every delivery. House balls are exempt from rule 7 and can be used by all bowlers.
RULE 9. If it is found that a bowling ball is or is suspected of being out of specification, the bowler must
be told by the tournament or league official to remove the ball from competition until it can be measured. If the ball is not removed or the bowler had prior knowledge of such, games are subject to forfeiture or disqualification. If the bowler had no prior knowledge, the games would not be subject to forfeiture, but the ball would not be able to be used until it meets specifications. If the bowler uses a ball that is non-conforming with knowledge that it is out of specification, the scores are subject to forfeiture and/or disqualification.
Further clarification on rule enforcement was provided by the USBC Rules department:
"The specifications regarding balance holes are now in the sixth season, but it seems leagues are still struggling with complaints regarding violations of the rule and how to handle them. USBC offers the following guidance:
If an individual is accused of violating this rule, the game is subject to forfeiture. As part of the process to determine what penalty would apply (if any) it should be determined in the bowler in question was previously informed of the rule. If it is determined they were unaware of the rule, the board could assess a warning instead of a forfeiture. If it is determined the player was aware of the rule but still violated it, the declaration of a forfeiture for the individual would be in order. In those situations, the PLAYER would receive a score of zero (0) for the game, but the scores of teammates wouldn't be affected. The board can determine to make the individual forfeit their games for the last 15 days.
For clarification purposes, a bowler would have to be able to insert enough of their finger/thumb into the holes to physically grip the ball for it to be considered a gripping hole being used for gripping purposes. Typically, the digit is inserted at least to the first knuckle, but we have noticed some bowlers insert their fingers/thumbs a little shallower than that. If the bowler can demonstrate they are able to hold the ball by their side and swinging it with that gripping orientation (with the holes on the top portion of the ball), that would be enough evidence to prove they are using the hole for gripping.
This grip would be used throughout the approach to delivery. Removal of the thumb/finger during the approach would make the bowling ball illegal."
