M2 Armament Group M2 Streamline Lower Receiver Completion Kit SOPMOD Black. Engineered for custom builders tactical armorers and shooters who refuse to compromise on quality this complete build bundle delivers every internal small part stock component and buffer extension hardware needed to turn a stripped lower into a fully functional hard-use foundation. Specifications for M2 Armament Group M2 Streamline Lower Receiver Completion Kit: Manufacturer: M2 Armament Group Color: Black Fabric/Material: Aluminum Caliber: Universal Gun Make: AR Platform Gun Model: AR-15 Gun Type: Semi-Automatic Rifle Trigger Pin Size: 0.154 in Weight: 40 oz Package Contents: M2 Armament Group M2 Streamline Lower Receiver Completion Kit M2 Armament Group M2-UPPER-C-OCT2: M2 Streamline Lower Receiver Completion Kit SOPMOD Black