The Ballastics Advantage 14.5″ 5.56 BA Hanson Midlength AR- 15 Performance Series Barrel with Lo Pro is machined from 4150 Chrome Moly Vanadium steel with a QPQ Corrosion Resistant Finish. The Performance Series Barrels feature a Nickel Boron Coated M4 feed ramp extension. Hanson Series Barrels feature our proprietary BA Hanson profile carbine gas system length 1.03″ gas block seat for .750″ low profile gas blocks only 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.