Complete 9mm upper receiver fitted with a Patriot Ordnance Factory Predator P-4 rail and 9" barrel. The T.R.O.S. silencer is attached using a Gemtech 3-lug mount. NOTE: This Silencer is a National Firearms Act (NFA), fully transferable Class 3, which is registered with the Bureau of Alcohol, Tobacco, Firearms and Explosives, (BATFE) under the provisions of 18 U.S.C. Chapter 44 and 27 CFR part 479.