The Ballastics Advantage 11.3" 5.56 BA Hanson Carbine Length 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, 1.00" gas block seat for .625" low profile gas blocks only and include a pinned lo-pro gas block. Hanson barrels are not designed to work with aftermarket piston kits.