Aero Precision M16A4 Clone Lower, Semi-automatic, 223 Rem/556NATO, Anodized Finish, Black APAR148017C The M16A4 Clone Lower Receiver features custom engraving on the AR15 Gen 2 Lower Receiver and is the perfect base for your M16A4 clone build. These lowers do not have engraving on the right side of the magwell.