Upper Receiver: A4 Flat-Top, Forged Barrel Length: 16″ Barrel Contour: M4 Barrel Material: 4150 Chrome Moly Vanadium Steel Muzzle Thread Pattern: 1/2″-28 Chrome Lined: No Barrel Finish: QPQ Melonite / Black Nitride Twist Rate: 1 in 7″ Chamber: 5.56x45mm NATO M4 Feed Ramps: Yes Bolt Carrier: Full-Auto Rated 1-Piece w/Integral Piston Strike Face Muzzle Device: A2 Flash Hider Gas System Length: Carbine, Short Stroke Piston Operated Gas Block Diameter: 0.750″ Handguard: M4 Handguards Sights: None Grip: A2 Grip Trigger: Standard G.I. Stock: 6-position Collapsible Weight: 6.2 lbs OAL: 32.5″ collapsed UPC: 812151023759 Lifetime Warranty: Yes