Barrel: 16" barrel length Chambered in 5.56 NATO, with a 1:7 twist, M4 barrel extension, and a carbine-length gas system. The M4 profile barrel is finished with Melonite. Barrel is finished off with an .750" diameter low-profile gas block, PSA 13.5" Lightweight M-Lok Free Float Rail and an A2 flash hider. Upper: Forged 7075-T6 A3 AR upper is hard coat anodized black for durability. Featuring M4 feedramp cuts, these upper upper receivers are made for us right here in the USA. Includes: MagpulA(R) MBUS Sight Set, Black BCG & Charging Handle Not Included.