The Ballastics Advantage 16" 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 . With a Lo Pro barrel profile and 1.03" gas block seat for .750" low profile gas blocks only. *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.