Diamondback Barrels. 5.56/223. Includes; Barrel, chrome-moly 1:7 (1/2x28tpi). Lower parts kit. Pistol tube assembly (buffer, end plate, castle nut, spring, & buffer). Crush washer and standard GI flash hider/muzzle brake. M4 upper receiver with Black phosphate AR-15 BCG. Gas tube and gas block. All you'll need is a rear grip, lower receiver, barrel nut & forearm. Made in U.S.A.