Grey Ghost Precision Billet Receivers are precisely machined from 7075-T6 Aluminum for a perfect fit with MKII Heavy Rifle Lowers but will also fit on most other AR-10 (DPMS) lower receivers on the market. Start your build off right. FeaturesUpper Receiver machined from a 7075-T6 Aluminum BilletTrue Black Type III Class 2 Hard Coat AnodizeTighter than Mil-Spec tolerance, with critical tooling dimensions are held to within + /- .001"Functions with nearly all available AR-10 DPMS pattern partsDPMS High Rail Height NotesDue to tightened tolerances of upper receiver, barrels may require thermal fitment. We recommend taking to a qualified gunsmith.DOES NOT include port door, forward assist or any small parts