The Jayhawk Measuring Ball has been the premier fitting tool in the bowling industry for over 40 years. The Jayhawk Measuring Ball is the only fitting system that allows the bowler to feel a grip BEFORE a ball is drilled. The recently rewritten instruction manual helps you easily fit every type of bowler using the latest techniques developed by IBPSIA, including the Pie Chart Formula. Our new inserts are made of urethane and give the same feel as the ball. New colorized finger and thumb parts for easy use Complete set of 36 inserts machine cut for accuracy Includes 2 metal span rulers One year warranty