Arsenal Inc AR-20 Muzzle Brake 7.62x39 / 5.56x45 Caliber 14x1mm LH Thread Black Oxide One Size AK-352US. 62x39mm or 5.56x45mm with 14x1mm LH threads. Stainless Steel with Black Oxide Finish. Specifications for Arsenal Inc AR-20 Muzzle Brake 7.62x39...