This bowling ball ships PRE-DRILLED. There are 5 sizes and the sizes that we drill are based on the weight of the ball. X-Small: 6lbs- Ages 8 and under, Small: 8lbs and 9lbs- Ages 8-11 and womens ring size from 8-11, Medium: 10lbs, 11lbs, and 12lbs, Ages 11-15 and Adult Ring size 10 or lower, Large: 13lbs and 14lbs, Mens ring size 10-12 or people with larger hands, X-Large: 15lbs and 16lbs, Mens ring size over 13 or people with extremely large hands. If you would like a different size drilled for the weight you selected, you must contact us via email as soon as your order is placed with your order number. Pre-Drilled bowling balls cannot be returned or exchanged. Storm is MIXing it up with the new Storm Mix. This ball is recommended for the bowler who needs a colorful spare ball. Since this is a urethane you may also prefer this ball as your strike ball since it works best on desert dry conditions. Mix things up a little and be the first to own the Storm Mix. The new Mix balls, available in two different colors, expand the Ice line with a new look and feel. The Mix, like the Polar Ice, features a durable U1S first generation urethane coverstock which is more controllable than U2S which powers the popular Natural series. The Mix traditional 3-piece core enhances predictability while the urethane coverstock ensures durability that other materials just cannot offer. And they are available in lighter weights. In addition to the standard 10-16 pound options, Storm is pleased to offer both 6 and 8 pound options as well. Coverstock: U1S Pearl Urethane Core: Traditional 3-piece Factory Finish: 3500-grit Polished Reaction: Low Recommended Lane Condition: Light