The Strike Industries AR Shim Set for .223/5.56 or .308 assists in timing and alignment of your muzzle devices for a piece of mind dependable installation. Crush washers are usually a one-time use washer designed to deform and do not guarantee alignment. Shim washers are flat, consistent and should be used whenever bore alignment is critical in applications such as silencer mounts or to ensure your muzzle device ports are correctly positioned. Available in both 1/2"-28 TPI (.223/5.56) or 5/8"-24 TPI (.308) sizes, the Strike Industries AR Shim Set for .223/5.56 or .308 are solid one-piece shims made in various precision thicknesses for just about any application.