The TacFire SSBU55610 AR15 upper is chambered in 5.56 NATO and features a 10.5-inch barrel with a Black Nitride finish. The 1:8 twist rate enhances bullet stability for improved accuracy and performance.Key FeaturesBarrel Length: Equipped with a 10.5-inch barrel.Barrel Finish: Finished in Black Nitride for enhanced durability.Caliber: Compatible with .223 Remington and 5.56 NATO cartridges.Rate of Twist: Features a 1:8 twist rate for bullet stability.