DPMS Kitty Kat Quad-Rail 5.56x45mm NATO 7.5 inch Upper Receiver One Size. 5in Chambered in 5.56 NATO with a 1:7 twist rate M4 barrel extension and a pistol length gas system. This nitride barrel is finished off with a DPMS Quad Rail free-float rail .750in diameter low profile gas block and an A2 flash hider. Upper: Forged 7075-T6 A3 AR upper is made to MIL-SPECS and hard coat anodized black for durability. These uppers are made for us right here in the USA by a mil-spec manufacturer. Bolt: Bolt is made of Mil-spec shot-peened Carpenter 158 steel. Gas key is secured with grade 8 fasteners and staked per mil-spec. Bolt carrier is parkerized outside and chrome lined inside. Specifications for DPMS Kitty Kat Quad-Rail 5.56x45mm NATO 7.5 inch Upper Receiver: Manufacturer: DPMS Caliber: 5.56x45mm NATO Barrel Length: 7.5 in 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: 6.5 in Barrel Material: Chrome Moly Vanadium Package Contents: DPMS Kitty Kat Quad-Rail 5.56x45mm NATO 7.5 inch Upper Receiver DPMS DP51655207090: Kitty Kat Quad-Rail 5.56x45mm NATO 7.5 inch Upper Receiver One Size