Barrel Shim Set to be used to correctly orient a timed muzzle device. This set is used with our 30 Cls Q.D. Muzzle Brakes. This shim kit has an inner diameter of 5/8" and is made of stainless steel. Included with this shim kit are shims with the following thicknesses: 2x 0.002" 5x 0.005" 1x 0.020" This shim kit has an inner diameter of 5/8"