Vise Inserts IT Top Sleeve, Ball IT and Ball IT Safety MollyThis kit includes 5 of each item – a top sleeve for your choice of a slug (1 1/8, 1 1/4 or 1 3/8), Ball IT, and Ball IT Safety Molly.This kit is used when drilling a brand new bowling ball using the Vise IT System.The Top Sleeve is installed at the top of your thumb hole to secure your IT thumb slug from excess movementThe Ball IT and Ball IT Safety Molly are placed at the bottom of your thumb hole to lock in the Vise IT thumb slug