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. Hammer is proud to offer the broadest range of core and cover options in bowling. We are excited to enhance the product line by adding a “big” shiny symmetric ball, the Hazmat. The Hazmat is a lower RG and higher Differential core that will help the ball pick up in the mid-lane and have a strong and continuous down-lane motion. The base cover is the extremely popular and highest-performing HK22, and we’ve used the Symtex Hybrid additives. The core and cover combination of the Hazmat creates a big hooking and never quitting ball motion that bowlers love to see. PERFORMANCE: Upper Mid COLOR: Black / Sapphire / Jade CORE: Hazmat COVERSTOCK: HK22 - Semtex Hybrid COVER TYPE: Hybrid Reactive FINISH: 500, 1000, 1500 Siaair / Factory Compound WEIGHTS: 16-12 Pounds LANE CONDITION: Medium oil REACTION: Length with strong backend WARRANTY: Two years from purchase date RG (16lbs)2.492 (15lbs)2.479 (14lbs)2.501 (13lbs)2.585 (12lbs)2.608 DIFF (16lbs)0.048 (15lbs)0.055 (14lbs)0.055 (13lbs)0.040 (12lbs)0.040