This 5.56 NATO chambered 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. Specifications for Ballistic Advantage 5.56x45mm NATO Hanson Cold Hammer Forged Threaded Barrel w/ Lo Pro: Manufacturer: Ballistic Advantage Finish: Phosphate Fabric/Material: Chrome Moly Vanadium Barrel Profile: Hanson Gas Block Journal Size-Diameter: .750 in Threads per Inch: 1/2x28 Barrel Twist Rate: 1-7 Flutes: No Gun Make: AR Platform Gun Model: AR-15 Package Contents: Ballistic Advantage 5.56x45mm NATO Hanson Cold Hammer Forged Threaded Barrel w/ Lo Pro What firearm models does the manufacturer say Ballistic Advantage 5.56x45mm NATO Hanson Cold Hammer Forged Threaded Barrel w/ Lo Pro is compatible with? The manufacturer says that Ballistic Advantage 5.56x45mm NATO Hanson Cold Hammer Forged Threaded Barrel w/ Lo Pro is compatible with AR-15