Turbo Grips introduces its popular Quad 4-N-1 insert in ALL sizes. Now available in 19 sizes. The Quad 4-N-1 insert combines 4 great styles, Power Oval, Perfect Oval, Round Mesh and Perfect Oval Mesh, into just one product. As an added plus, each Quad insert is designed with a patented Glue Groove to minimize excessive adhesive from seeping to the surface of the ball during installation. Durometer Hardness 40 Shore A 31/32 O.D. (outside diameter)