Windham Weaponry 20" A2 gov't profile barrel. 4150 Chrome Moly Vanadium 11595E steel, chrome lined, chambered in 5.56, 1/7 twist, rifle length gas system, 1/2" x 28 muzzle thread, black manganese phosphate finish.
Includes the barrel extension (with M4 feed ramps), barrel nut, triangular front handguard cap, standard A2 front sight base with sling swivel, and bayonet lug.