The overthrow is an open mag well helmet design, with battle worn dents, sword gashes and crack lines.It is machined top to bottom from 7075-t6 aluminum with a multi caliber mark.The overthrow is fully compatible with all mil-spec internal parts and other aftermarket mil-spec upper receivers, and gi standard issue magazines as well as pmags.Type: Lower ReceiverGun Model: AR-15Gun Type: AR PlatformCaliber: Multi-CaliberMaterial: 7075 AluminumFinish: Black Hardcoat Anodized