FN America Ar15 Midlength Barrel . 56x45mm. Styled To Reflect The M16 Platform And Made From Strong Mil-spec Steel With Black Manganese Phosphate Finishing This 16 Button Rifled Fn America Barrel Is An Ideal Choice For Any Mid Length Ar-15 Rifle. Chambered In .223 Rem / 5.56x45mm The Chrome Lined Chamber With Its Feed Ramp Will Provide More Consistent And Reliable Feeding While Shooting. Package Contents: FN America Ar15 Midlength Barrel