CMC Triggers AR-15 Tactical Short 5.56 Nato Threaded AR Barrel w/Gas Block/Gas Tube 11.5in 1-7 Twist Carbine Length 1/2x28 TPI Nitride Black Medium. That's what this 11.5-inch barrel gives you. It sits in a nice middle spot: still short enough for tight quarters long enough to pull solid velocity from 5.56 NATO. The 1:7 twist handles heavy bullets without trouble. Government profile non-fluted and finished in black nitride so it shrugs off moisture. Muzzle threads are 1/2x28 TPI. Gas block and gas tube are included which saves you a separate order and gets the build moving faster. Specifications for CMC Triggers AR-15 Tactical Short 5.56Nato Threaded AR Barrel w/Gas Block/Gas Tube: Manufacturer: CMC Triggers Color: Black Finish: Nitride Fabric/Material: 4150 Chrome Moly Vanadium Caliber: 5.56x45mm NATO Barrel Length: 11.5 in Barrel Profile: Government Gas System Length: Carbine Length Gas Block Journal Size-Diameter: .750 in Barrel Twist Rate: 1-7 Barrel Material: 4150 Chrome Moly Vanadium Flutes: No Gun Make: AR Platform Gun Model: AR-15 Firearms Threads Per Inch: 1/2x28 Package Contents: CMC Triggers AR-15 Tactical Short 5.56Nato Threaded AR Barrel w/Gas Block/Gas Tube Includes gas block and gas tube What firearm models does the manufacturer say CMC Triggers AR-15 Tactical Short 5.56Nato Threaded AR Barrel w/Gas Block/Gas Tube is compatible with? The manufacturer suggests that CMC Triggers AR-15 Tactical Short 5.56Nato Threaded AR Barrel w/Gas Block/Gas Tube is compatible with AR-15CMC Triggers CMC-BBL-556-115C-GB: AR-15 Tactical Short 5.56 Nato Threaded AR Barrel w/Gas Block/Gas Tube 11.5in 1-7 Twist Carbine Length 1/2x28 TPI Nitride Black Medium