Note TACSHIM 1/2x28 barrel shim kit have two different OD available. OD .748” shim kit is designed for .223 5.56 9mm barrel with common .750” barrel OD. Special OD .625” shim kit is compact designed for some 9mm barrel with special OD (smaller than common .750") at the Min Barrel O.D.. Please check the fitment before ordering. TACSHIM will be an ideal and new solution for you, whether you've tried the thread locker/crush washer/peel washer or not. TACSHIM offers a far greater degree of precision than that of any crush washer or peel washer, also let you being faster and less labor intensive to install correctly. Tips: TACSHIM shims can be used alone or in different combinations. This is just a game of trial and error to get your desired thickness.