M2 Armament Group AR-15 Standard Upper Receiver Black. Eliminate the hassle of installing tiny roll pins and high-tension springsthis high-grade upper comes 100percent factory assembled in the USA with a mil-spec ejection port dust cover door and forward assist mechanism pre-installed and function-checked. Specifications for M2 Armament Group AR-15 Standard Upper Receiver: Manufacturer: M2 Armament Group Color: Black Fabric/Material: 7075-T6 Aluminum Gun Make: AR Platform Gun Model: AR-15 Gun Type: Semi-Automatic Rifle Barrel Material: 4150 Chrome Moly Vanadium Magazine Included: No Handguard Type: Free-Float Gun Rail: Free Float M-LOK Package Contents: M2 Armament Group AR-15 Standard Upper Receiver What firearm models does the manufacturer say M2 Armament Group AR-15 Standard Upper Receiver is compatible with? The manufacturer suggests that M2 Armament Group AR-15 Standard Upper Receiver is compatible with AR-15M2 Armament Group M2-UPPER-BUILT: AR-15 Standard Upper Receiver Black