Our 4.25” muzzle brake is fully machined with an inner expansion chamber for maximum gas distribution. It also features heavy-duty steel construction that will hold up to repeated use. This brake works with the standard M14x1LH barrel thread pitch and can be permanently attached to an AMD barrel to acquire legal 16-inch length. Fits all AK variants with a threaded barrel. This item is marked as “ USA ” and counts as 1 U.S. Sec 922R compliant part.