The Spike's Tactical ST-15 upper line-up is designed as a fully Mil-spec compliant upper series for law enforcement. This same level of quality and performance is now available to everyone, all at a price range that is affordable to shooters of any budget. Each component is manufactured to Mil-spec standards. This model features Spike's Tactical 16" with 1:7 Twist Mil-spec Barrel, M4 Barrel Profile, Carbine Length Gas System, ST Micro Gas Block, .750" Diameter Gas Seat, Spike's Tactical Mil-Spec M16 Bolt Carrier Group, ST BAR rail system, and A2 Flash Hider.