The Down Range Products muzzle device alignment set is made to use instead of a peel washer normally used with muzzle brakes and suppressors. The kit allows you to properly time your muzzle device so it will be positioned the way you desire on your rifle or threaded barrel handgun. Included are three different size shims. 1 Large .02 Thick. 4 medium .008 Thick. 4 small shim .004" Thick. The large shim is for 1/2 rotation adjustment as well as barrels with no thread relief cut. the medium shims give you 45 degrees rotation per shim. The small shim gives you fine adjustment. Outside Diameter. .75" Inside Diameter. .515" It coated with a black Oxide finish. This set is made from high quality Stainless Steel in the USA! These are for 1/2 - 28 threaded barrels. Instructions included.