Ballistic Advantage Classic Series Chrome Lined Barrel M4 Profile 5.56 x 45mm 14.5 inch 1-7 Twist 1/2x28 Threaded Phosphate Black. 56 chambered 14.5 inch M4 Carbine Length Classic Series Barrel is machined from CrMoV steel with a chrome lined bore and chamber with a manganese phosphate finish and phosphate coated M4 feed ramp extension. Specifications for Ballistic Advantage 5.56 x 45mm M4 Profile Classic Series Chrome Lined Barrel: Manufacturer: Ballistic Advantage Color: Black Finish: Phosphate Caliber: 5.56x45mm NATO Barrel Length: 14.5 in Barrel Profile: M4 Gas System Length: Carbine Length Gas Block Journal Size-Diameter: .750 in Threads per Inch: 1/2x28 Barrel Twist Rate: 1-7 Barrel Material: Chrome Moly Vanadium Flutes: No Gun Make: AR Platform Gun Model: AR-15 Weight: 25 oz Condition: New Gas Block Journal Size-Length: 0.75 in Country of Origin: USA Package Contents: Ballistic Advantage 5.56 x 45mm M4 Profile Classic Series Chrome Lined Barrel What firearm models does the manufacturer say Ballistic Advantage 5.56 x 45mm M4 Profile Classic Series Chrome Lined Barrel is compatible with? The manufacturer suggests that Ballistic Advantage 5.56 x 45mm M4 Profile Classic Series Chrome Lined Barrel is compatible with AR-15Ballistic Advantage BABL556009MC: Classic Series Chrome Lined Barrel M4 Profile 5.56 x 45mm 14.5 inch 1-7 Twist 1/2x28 Threaded Phosphate Black