Barrel: 10.5" chrome moly vanadium steel barrel. Chambered in 9mm (9x19), with a 1/10 twist rate. The barrel is nitride treated for durability and finished off with a PSA 9" Lightweight M-Lok Rail, and an A2 Flash Hider Upper: Newly designed 6061 Billet T6 Aluminum slick side upper is hard coat anodized black for durability.  Featuring T-marks, these upper receivers are made for us right here in the USA. Bolt Carrier Group: Gen 4 Hybrid 9mm BCG.  Nitride treated 8620 steel bolt, with an enhanced firing pin and external 5.56 style extractor. The bolt carrier group is compatible with most aftermarket fire control groups.  Build Kit: A high quality lower build kit with everything you need to assemble your AR-9 lower into a pistol. Features Mil-Spec Fire Control Group, Magpul Grip, Magpul Trigger Guard, and black oxide coated hammer and trigger springs. Also includes SB Tactical SBA3 Adjustable Pistol Brace, castle nut, latch plate, carbine buffer spring, 5 positioning mil-spec buffer tube, and 9mm buffer.#html-body [data-pb-style="62DF828A6A3EB"]{justify-content: flex-start; display: flex; flex-direction: column; background-position: left top; background-size: cover; background-repeat: no-repeat; background-attachment: scroll; border-style: none; border-width: 1px; border-radius: 0px; margin: 0px 0px 10px; padding: 10px;}#html-body [data-pb-style="62DF828A6A3F8"]{border-style: none; border-width: 1px; border-radius: 0px; margin: 0px; padding: 0px;}