The SRD556 is an Inconel 718 direct thread suppressor. Inconel 718, a nickel alloy stainless steel, provides the highest level of durability, particularly with short-barreled hosts using supersonic ammunition. The 1/2x28tpi threads match the vast majority of modern rifles in .223/5.56mm on the market today. The rear mount has wrench flats to torque the suppressor to the barrel. These wrench flats can be used as a location to pin and weld the suppressor to make a shorter barrel over 16 in total length. Requires a Class 3/SOT for purchase