Caliber: 5.56x45mm NATO - Operation System: Direct Gas Impingement - Barrel Length: 20 - Barrel Type: Heavy Barrel - Twist Rate: No - Barrel Material: 4140 Chrome Moly - Barrel Features: M4 Feedramps Black Nitride Finish - Sight / Gas Block: F Marked Front Sight - Muzzle Device: A2 Flash Hider - Handguard: RIFLE HANDGUARD - Upper Receiver Type: Flattop - Upper Receiver Material: Forged Aircraft 7075 T6 Aluminum - Upper Receiver Coating: Anodized to Mil-Spec - Upper Receiver Features: Brass Deflector M4 Feedramps T-Marks Forward Assist Dust Cover