This is a Yankee Hill Machine Co Part known as the Shim Set, model SHIM-3102-SET.
Barrel Shim Set to be used to correctly orient a timed muzzle device. This set is used with our 5.56mm Q.D. Muzzle Brakes. This shim kit has an inner diameter of 1/2"
Features:
Thicknesses included 2x 0.002, 3x 0.005, 1x 0.020"
