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. The new Hammer Effect is unlike any other; it is the first ball to be poured in four colors. The gorgeous appearance isnΓÇÖt the only thing that will turn heads; the Hammer EffectΓÇÖs clean and aggressive mid-lane and backend performance is unparalleled in the High Performance category. The Hammer Effect introduces a new core shape called Huntsman and has physical features that will remind you of other famous Hammer balls like the Vibe and Black Widow, creating optimum performance on the lanes. Along with the new core, weΓÇÖve upped our HK22 game with this new version that takes responsiveness to the next level. Once you see what the Hammer Effect does on the lanes, youΓÇÖll want HK22 ΓÇô Cohesion Pearl to be used more and more. Performance: High Color: Maroon/Blue/Black/Purple Core: Huntsman Coverstock: HK-22 Cohesion Pearl Cover type: Pearl Reactive Finish: 500, 1000, 1500 Siaair/ Facotry Compound Weights: 12-16lbs Reaction: Aggressive Mid-lane and backend Lane Condition: Medium To Heavy Oil Warranty: 2 Years from purchase date RG: 16lbs (2.483) 15lbs(2.470) 14lbs(2.495) 13lbs(2.597) 12lbs(2.593) Diff: 16lbs(0.043) 15lbs(0.050) 14lbs(0.050) 13lbs(0.041) 12lbs(0.041) ASY: 16lbs(.015) 15lbs(.017) 14lbs(.016) 13lbs(.014) 12lbs(.014)