Barrel: 8" chrome-moly steel barrel. Chambered in 9mm, (9x19), with a 1/10 twist. The barrel is nitride treated for durability and finished off with a Palmetto State Armory7" Lightweight Hex Full Picatinny M-Lok Free Float Rail and a birdcage style A2 flash hider. Upper: Billet 6061-T6 Slick side AR upper is hard coat anodized black for durability. 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. Lower: Forged 7075 T6 aluminum and then hard coat anodized, these lowers are purpose-built to accept 9mm GlockA(R)-style magazines. Designed to work with PSA's new 9mm Hybrid uppers. The lower is assembled with a Palmetto State Armory MOE SBA3 lower build kit with a Magpul MOE Grip, PSA 6 position buffer tube, and SBA3 Adjustable Brace. Does not include last round bolt hold-open feature. *PSA Can't Guarantee Function With EndoMag 9mm Magazines