The following information was circulated by World Bowling for adherence to the Ball Specification Rule:
The Technical Committee recommended certain revisions to the ball specifications, with effective dates starting January 1, 2019. The recommendation was considered by the Executive Board, which unanimously approved the following rule changes (in red), which are effective until the 2019 Congress has the opportunity to ratify or reject:
11.12 Drilling specifications
11.12.1 The following limitations, as specified, shall govern the drilling of holes in the ball.
11.12.2 Holes or indentations for gripping purposes shall not exceed five and shall be limited to one for each finger and one for the thumb, all for the same hand. The player is not required to use all finger holes in any specific delivery, but they must be able to demonstrate, with the same hand, that each gripping hole can be simultaneously used for gripping purposes. Any thumb hole that is not used for gripping purposes during the delivery would be classified as a balance hole.
11.12.3 (until August 1, 2020), One hole for balance purposes not to exceed 1 ¼ inch (31.8 mm) diameter. (Including the surface opening).
11.12.4 No more than one vent hole to each finger and/or thumb hole not to exceed ¼ inch (6.4 mm) in diameter. (Including the surface opening).
11.12.5 One mill hole for inspection purposes not to exceed 5/8 inch (15.9 mm) in diameter and 1/8 inch (3.2 mm) in depth.
11.13.1 The following tolerances shall be permissible in the balance of a bowling ball used in sanctioned competition.
11.13.2 A. Weight more than 10 pounds (4.53 kg)
a) Not more than 3 ounces (85 grams) difference between the top half of the ball (gripping holes side) and the bottom half of the ball (side opposite the gripping holes).
b) (not valid on or after August 1, 2020), Not more than 1 ounce (28 grams) difference between the half of the ball to the left and the half of the ball to the right of the center of grip (side weight).
c) (not valid on or after August 1, 2020), Not more than 1 ounce (28 grams) difference between the half of the ball toward the thumb hole side of the center of grip and toward the finger holes side of the center of grip (thumb/ finger weight).
11.13.3 For balls without a balance hole not more than 3 ounces (85 grams) between any two halves of the ball. A ball used without any gripping holes or indentations may not have more than 3 ounces (85 grams) of difference between any two halves of the ball. The effective date for this revision is January 1, 2019; if a World Bowling or Zone event finishes on or after January 1, 2019 then 11.13.3 applies to the entirety of that event.
Subsequently for the World Junior Championships in Paris in March 2019, both old and new rule can be applied.