The yhm lowers are machined 100% in house from forged 7075-t6 aircraft grade aluminum.They feature over sized magazine well chambers for easier magazine changes.They will accept all generations of pmag's and mil-spec upper receivers.They fit all standard parts and are finished in hardcoat anodized matte black to military specifications or better.Type: Lower ReceiverGun Model: AR-15Gun Type: AR PlatformCaliber: 223 RemMaterial: 7075 T6 AluminumFinish: Matte Black Hardcoat AnodizedTrigger: None