This premium grade AR-15 Barrel is a 16\" M4 Contour profile barrel made of 4150 chrome moly vanadium with a black nitride finish, a carbine length gas system with a 1:8 twist rate. The barrel is chambered in 5.56 NATO and machined with M4 feed ramps in the barrel extension. All Finished Barrels go through a 100% Inspection Process. Inspections Equipment includes CMMs and Air Gauges for the Bores.