Yankee Hill Machine Co Shim Set, 5/8 Inside Diameter, Fits .30 Caliber QD Muzzle Breaks SHIM-3302-SET Barrel Shim Set to be used to correctly orient a timed muzzle device. This set is used with our 7.62mm Q.D. Muzzle Brakes. This shim kit has an inner diameter of 5/8"