Dark Storm Industries DS-15 AR-15 Typhoon 5.56x45mm NATO 12.5inch Upper Receiver. Caliber 5.56x45mm NATO. Barrel Length 12.5 in. Barrel Profile SOCOM. Gas System Length Carbine. Barrel Twist Rate 1-7. Finish Cerakote. Handguard Length 10 in. Gun Make AR Platform. Gun Model AR-15. Barrel Material Steel. Bolt Carrier Group Included MIL-SPEC. Charging Handle Included MIL-SPEC. Package Contents: DS-15 AR-15 Typhoon 12.5inch Upper Receiver.