Product Description The Turbo Grip Fitter helps bowlers find the perfect fit between the 19 sizes available in the Quad Insert line.Size Increments are 1/64″- Standard O.D. of 31/32″-for sizes 19/32″ thru 13/16″- Larger O.D. of 53/64″-for sizes 29/32″ thru 1-1/32″The Quad Soft 4-N-1 insert combines 4 great styles: Power Oval, Perfect Oval, Round Mesh and Perfect Oval Mesh.