Luth-AR 5.56 Lightweight Barrel Carbine 1-9 Twist 1/2 x 28 Black. Specifications for Luth-AR 5.56 Lightweight Barrel: Manufacturer: Luth-AR Color: Black Finish: Phosphate Fabric/Material: 4140 Chrome-Moly Caliber: 5.56x45mm NATO Barrel Length: 16 in Barrel Profile: Light Weight Gas System Length: Carbine Length Gas Block Journal Size-Diameter: .750 in Threads per Inch: 1/2x28 Barrel Twist Rate: 1-9 Barrel Material: 4140 Chrome Moly Vanadium Flutes: No Gun Model: AR-15 Weight: 1.12 lb Features of Luth-AR 5.56 Lightweight Barrel 6 Lands and Groves M4 Feed Ramp Button Broached Package Contents: Luth-AR 5.56 Lightweight Barrel What firearm models does the manufacturer say Luth-AR 5.56 Lightweight Barrel is compatible with? The manufacturer says that Luth-AR 5.56 Lightweight Barrel is compatible with AR-15Luth-AR BL-L16: 5.56 Lightweight Barrel Carbine 1-9 Twist 1/2 x 28 Black