The Rock River Arms RRAGE 3G Complete Upper is a streamlined 5.56x45mm NATO assembly designed for the AR-15 platform. It features a 16 chrome moly steel barrel with a 1:8 twist and a black finish. The black extruded aluminum A4 receiver is a slick-side design with a port door and no forward assist, reducing bulk and weight to 4.25 lbs. This unit includes a 15 RRAGE 3G M-LOK handguard, a carbine-length gas system with a low-profile gas block, and an A2 Flash Hider on a 1/2-28 thread. It comes fully equipped with a bolt carrier group and charging handle. Note: The 5.56mm NATO chambering is designed to safely and reliably cycle both 5.56x45mm NATO and .223 Remington ammunition.