5.56mm 18" Cold Hammer Forged, Twist Rate 1:7, Muzzle Thread 1/2x28 TPI (Threads Per Inch), Chrome Moly Vanadium, Outside Finish Mil-Spec Heavy Phosphate, Mid-length Gas System, .750″ Diameter At Gas Port, S2W (Strength-to-Weight) Profile, 2.65lbs.