These stainless steel washers are precisely machined to within .0001" to allow accurate indexing of muzzle brakes and flash hiders without the need for peel or crush washers. Set includes 18 individual washers of different thicknesses to allow 360 degree timing in 20 degree increments. Only one washer is needed for each application. Mfg: Precision Armament SPECS: Stainless steel, matte gray finish. Set available for 5/8" x 24 threads. Set includes 18 washers and instructions.