DPMS M-Lok 5.56x45mm NATO 11.5 inch Upper Receiver One Size. 5in 4150V Chrome Moly vanadium steel phosphate coated and chambered in 5.56 NATO with a 1 in 7in twist. Carbine-length gas barrel is finished off with a DPMS Lightweight 10.5in M-Lok rail a low profile gas block and a PSA A2 Flash Hider. Upper: Forged 7075-T6 A3 AR upper is made to MIL-SPECS and hard coat anodized black for durability. Featuring a mil-spec finish these uppers are made for us right here in the USA by a mil-spec manufacturer. Bolt Carrier Group: Bolt made of mil-spec shot-peened Carpenter 158 steel. Gas key is secured with grade 8 fasteners and staked per mil-spec. Specifications for DPMS M-Lok 5.56x45mm NATO 11.5 inch Upper Receiver: Manufacturer: DPMS Caliber: 5.56x45mm NATO Barrel Length: 11.5 in Gas System Length: Carbine Length Barrel Twist Rate: 1-7 Threads per Inch: 1/2x28 Muzzle Device: A2 Fabric/Material: 7075 T6 Aluminum Gas Block Journal Size-Diameter: .750 in Handguard Length: 10.5 in Barrel Material: Chrome Moly Vanadium Bolt Carrier Group Included: MIL-SPEC Charging Handle Included: MIL-SPEC Package Contents: DPMS M-Lok 5.56x45mm NATO 11.5 inch Upper Receiver DPMS DP51655130076: M-Lok 5.56x45mm NATO 11.5 inch Upper Receiver One Size