Based on the supremely popular 737R, the Impact Precision NBK brings you everything you love about Impact's flagship 737R in a lightweight setup ideal for your next hunting rifle. The Impact NBK utilizes the same barrel tenon/headspace specs as the 737R and can readily accept 737R prefit barrels. FeaturesAluminum Shroud and BodyIntegral Recoil Lug20 MOA RailCompatible with AICS and AW MagazinesMini M16 ExtractorOne Piece Bolt Design90 Degree Bolt Throw Note: Will NOT work with BDL hardware.