Vise Lady P/S Finger Inserts (Power Lift/Semi) – 5 Pack GripsOne side of the insert is a Semi cut and the other side is a Power LiftThe Power Lift helps the bowler create more revs with the 1/4″ forward pitch that aids grip.The semi side provides a bump for additional grip when inserting your finger past the first joint.Drill bit size required: 7/8Vise P/S Inserts are available in 16 sizes and 7 colors.Sizes 17/32 through 3/4 have O.D. of 7/8″