The Noveske N6 Stripped Upper Receiver is a Mil-Spec flat-top large frame upper. It is designed for the Noveske N6 line of LARGE frame receivers and will not work with AR-15 (N4) SMALL frame parts. The N6 Upper Receiver comes equipped with a shell deflector. FeaturesPicatinny mil-standard 1913 top rail with Noveske CrossFeaturing anti-rotation interface with handguard now with two anti-rotation pinsReceiver designed to match the profile of Noveske N6 4th Generation handguardsN6 barrel nuts are threaded 1 7/16x 16 TPI