The Luth-AR 16" Lightweight Complete Upper is a ready-to-install AR-15 upper receiver assembly in .223 Remington. Drop it onto a compatible AR-15 lower and the upper half of the rifle is done. It starts with a 16" lightweight .223 Remington barrel made from 4140 chromoly steel with a 1:9 twist. The barrel is mated to an assembled A3 flattop upper receiver that includes a bolt carrier, charging handle, forward assist and ejection port cover. A low-profile gas system sits under an ergonomic 15" Palm handguard with KeyMod slots and a Picatinny top rail. What's included: HG-V-15K Palm handguard, vented 15" KeyMod, with barrel nut BAA3-L16 16" lightweight barrel, .223 Remington, 4140 chromoly, 1:9 twist FTT-EA1 A3 upper receiver, assembled, with forward assist and ejection port cover BC-A-223 fully assembled bolt carrier, .223 UR-19 charging handle Low-profile gas system Fit check: this upper fits mil-spec AR-15 lower receivers. The barrel is chambered in .223 Remington, so use .223 Remington ammunition. The flattop has no fixed sights, so plan on an optic or flip-up sights for the top rail. Have headspace verified by a qualified gunsmith before first firing, then function-check the rifle and run a short break-in with quality ammunition.