This 5.56 NATO chambered 11.5 inch Cold Hammer Forged barrel is machined from CrMoV steel with a manganese phosphate finish and chrome lined bore. Our limited run of Cold Hammer Forged barrels feature an M4 Feed Ramp Extension and are HP and MPI tested. Hanson Series Barrels feature our proprietary BA Hanson profile and include a pinned lo-pro gas block. Hanson barrels are not designed to work with aftermarket piston kits. All NFA/ATF Rules Apply You may use this barrel with a lower receiver that is a Registered SBR, Machine Gun, or Pistol. Possession of this barrel along with a Non-NFA lower receiver is Prohibited, except when installed on a Pistol configuration firearm. Mfg: Ballistic Advantage