Features:Barrel: Harrington & Richardson 20" 5.56 NATO 1/12 Pencil Barrel made from 4150 Chrome Moly Vanadium Steel with a parkerized finish with chrome lining. Features a Rifle Barrel Extension 1/2"x28 threaded barrel 1/12 twist rate and Rifle gas system. Upper: Newly manufactured uppers forged from 7075-T6 Aluminum using proprietary NoDak Spud Dies. Finished in black anodizing. Lower: Made from forged aluminum and equiped with the Retro H&R FCG and A1 furniture this lower is classic in style and performs like an American Classic should.Details: Caliber: 5.56 NATO Barrel Length: 20" Barrel Profile: Pencil Barrel Steel: 4150 Chrome Moly Vanadium Barrel Finish:Parkerized Chrome Lining:Yes Muzzle Thread Pattern: 1/2" x 28 Twist Rate: 1/12 Barrel Extension: Rifle Gas System Length: Rifle Diameter at Gas Block: .625" Gas Block Type: Rifle Height Front Sight Base Muzzle Device: A1 style Receiver Material: Forged 7075-T6 Upper Receiver Type: M16A1 w/o feed ramps Handguard Type: M16A1 Triangular with heat Shields Bolt Material: Carpenter 158 Steel Bolt Carrier Profile: Full Auto Overall Length: 30 inches Grip: A1 Style Finish: Black Anodized Trigger:H&R Retro Trigger Features: Retro Flat Trigger Guard