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. Roto Grip Attention Star Bowling Ball Features: Ordinary? Far from it. Revolutionary? Absofrigginlutely right it is. Not only is Roto Grip presenting you with the most advanced core technology since the invention of sliced bread, but they also decided what the heck, why not just mix in an inner block design never before released domestically. Yeah, you read that correctly, prior to this out of this world concoction from their R&D lab, the original Momentous™Core was exclusive to our international market. But after countless seconds, minutes, hours, days and weeks of computer research and testing, Roto Grip figured out that density changes to this particular block and slug when placed in A.I. Core technology provided them with a motion they hadn’t seen before. And after multiple on lane tests, it was a quick and easy decision that they just had to wrap this baby with the time tested and proven eTrax PLUS Pearl Reactive coverstock to give you all an overall reaction unlike anything offered on earth today. Color: Berry/Silver/Iron Coverstock: eTrax PLUS Pearl Reactive Core: Momentous AV + A.I. Core Finish: Reacta Gloss RG: 2.48 (for 15# ball) Differential: 0.049 (for 15# ball) Recommended Lane Condition: Medium Oil Hook Potential: High Length: Late