This kit lets you pick out a lower of your choice along with a couple small parts to help complete your build! This kit boasts the Brownell's exclusive complete upper receiver, the Brownell's M4 stock assembly, and DPMS Lower Parts Kit. This Brownells’ exclusive Complete AR Upper Receiver is Made in the USA. Chambered in 5.56x45mm NATO and featuring a 16” barrel with a 1:8 twist. The standard A3 13-slot aluminum flat top receiver comes with a 10” handguard utilizing the KeyMod rail system. A low profile gas block, bolt carrier group, charging handle, forward assist, ejection port cover and phosphate finish help to complete this outstanding package. This complete A3 upper receiver will attach to almost any standard AR-15 lower receiver. Collapsible buttstock similar to the current US GI M4 carbine stock provides convenient six-position length-of-pull adjustment to fit different-size shooters, including those wearing body armor. Ready to install on any standard AR-15 rifle or carbine lower receiver; includes buffer tube, receiver lock plate, lock nut, toe-mounted steel sling loop, carbine recoil spring and buffer. Buttstock is made from extremely tough, fiberglass-reinforced, injection-molded nylon to resist impact, heat, moisture, extreme cold, and most cleaning solvents. Steel lock nut has four square notches and pre-cut detents for staking to lock plate. Available with Mil-Spec (nominal 1.14" O.D.) receiver extension tube. Stock interior diameter is matched to buffer tube O.D. for a snug fit that eliminates unwanted play and rattles. The easiest way to stock and sell genuine, mil-spec AR-15 parts, or use to assemble rifles on your receivers. Much lower in total cost than buying the parts one at a time. Kit contains only new, current-production, genuine, mil-spec parts; never pull-offs or direct-exchange surplus. Lower Receiver Parts Kit includes trigger spring, trigger pin, hammer spring, hammer pin, disconnector and spring, bolt catch, bolt catch plunger, bolt catch spring, bolt catch roll pin, selector, selector detent, selector detent spring, (2) takedown detents and springs, pivot pin, rear takedown pin, buffer retainer and spring, magazine catch, button and spring, screw and washer, triggerguard assembly, pin, hammer, trigger and pistol grip.