ATTENTION !!!!!!!!  New regulations on thumb and balance holes.  The rule eliminating balance holes in bowling balls takes effect Aug. 1, the start of the 2020-2021 bowling season. The rule states all holes in a bowling ball must be used on every delivery; any hole not used is considered a balance hole, making the ball illegal. Bowlers who do not use their thumb no longer can have a thumb hole, as it now is considered a balance hole. They also need to mark their ball to show where they place their palm on delivery. NBF sporting regulations  Article 717. Holes.  1. 1. The following rules shall apply with regard to holes in the ball:  a.  A maximum of 5 holes and/or dents for holding the ball are permitted, 1 for each finger and 1 for the thumb, all for the same hand finger and 1 for the thumb, all for the same hand. The player must be able to prove that he is using each of  The player must be able to prove that he is using each of these holes to hold and throw the ball, with the same hand. Any hole that is not is not used for holding and throwing the ball is regarded as a balance hole (see (b) below).  b. Balance holes are not allowed.  c. Bowling balls without a thumb hole must have an engraved cross (“+”) at the height of the centre of the palm. During the throw the palm shall cover the (“+”).  d. There is one air hole allowed per finger and/or thumb hole with a maximum diameter of 1/4 inch (rounded off 0,64 centimeter).  e. A maximum of one milled hole for inspection purposes is allowed with a diameter of maximum 5/8 inch (rounded 1.59 centimetres) and a depth of maximum 1/8 inch (rounded 0.32 centimetres).  2. The holes in the ball may be filled up for the purpose of re-drilling, among other things of the ball. The same provisions as in Article 716(2) and Article 232(1) and (2) apply with regard to filling.  232, paragraphs 1 and 2.  3. It is permissible to insert objects into the finger and/or thumb holes that are intended to change the span or the size of these holes, provided that these objects are inserted in such a way that they remain firmly in place during and after the throw.