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 Brunswick Rhino Reactive bowling balls are the perfect bowling ball for those looking at getting into their first reactive resin ball or for those looking for a ball for lighter to medium oil conditions. The new R-16 reactive coverstock describes our latest formulation that provides a perfect balance between power and control. The R-16 formula produces easy length and backend hook motion without extreme sensitivity to the dry and oily parts of the lane. The traditional light bulb core shape delivers outstanding ball motion and impressive pin action for more strikes and higher scores. The Rhino can be drilled using the standard drilling techniques developed for symmetric bowling balls. At Brunswick, the unique core shape of each individual ball is used for weights from 12 to 16 pounds. This approach to lightweight ball engineering provides bowlers with consistent ball reaction characteristics across this weight range. Core Type: Light Bulb Coverstock: R-16 Reactive Finishing Steps: 500 Siaair/Royal Compound/Royal Shine Weights: 10-16 Pounds RG Max: 2.554 RG Min: 2.524 RG Differential: 0.030