AT3 Tactical 5.56 NATO Pencil Profile 16 Inch AR-15 Barrel Black. 9-inch 5.56 NATO barrel features a midlength gas system for smoother recoil. This Pencil profile barrel uses 4150 CMV steel per Mil-B-11595E with a corrosion-resistant black nitride finish for enhanced longevity. If youre looking to upgrade from an M4 style carbine length system or building from scratch this barrel will perform for you. Specifications for AT3 Tactical 5.56 NATO Pencil Profile AR-15 Barrel: Manufacturer: AT3 Tactical Color: Black Caliber: 5.56x45mm NATO Barrel Profile: Pencil Gun Make: AR Platform Gun Model: AR-15 Package Contents: AT3 Tactical 5.56 NATO Pencil Profile AR-15 Barrel What firearm models does the manufacturer say AT3 Tactical 5.56 NATO Pencil Profile AR-15 Barrel is compatible with? The manufacturer suggests that AT3 Tactical 5.56 NATO Pencil Profile AR-15 Barrel is compatible with AR-15AT3 Tactical AT3-556-PEN-MID-16: 5.56 NATO Pencil Profile 16 Inch AR-15 Barrel Black