Compensator features a large initial expansion chamber which dissipates combustion gases at a lower pressure, then directs the gases to the side and rear through precisely canted vents. Innovative reverse venting design reduces recoil and blowback while eliminating muzzle rise. Closed bottom in compensator greatly diminishes dust signature. Machined from high strength stainless steel for corrosion resistance, compensator will not erode due to the extreme heat of automatic fire. Requires use of Accu-Washers sold seperately for proper installation. Mfg: Precision Armament SPECS: HTSR 416 stainless steel bar stock, matte black or in-the-white stainless steel finish. 1/2-28 TPI thread. 2.25" (5.2cm) OAL. 0.875" (2.2cm) dia. 2.6 oz (73.7g) wt. Fits .223 Cal (5.56mm) caliber. A04020 and A04021 fit .308 caliber and have 5/8x24 threads.