Premium Grade Parkerized AR-15 Rifle Barrel, 16\" M4 Contour Barrel, 1 in 9 twist. Gas port drilled for carbine length gas, threaded for compensator. Barrel extension in rear with M4 feed ramps. Gas port diameter .070\" at carbine length. Gas block diameter .750\". Caliber: 5.56 NATO. Finish: Parkerized. Material: 4140 steel. Weight: 1.90 lbs. Not chrome lined. Made in United States.