Barrel: 16" 4150V Chrome Moly Vanadium steel barrel, chambered in 5.56 NATO, with a 1:7 twist, M4 barrel extension, and a Mid-length gas system. The barrel is finished with with a .750" diameter low-profile gas block, PSA 13" Quad Free Float Rail and an A2 flash hider.Upper: Forged 7075-T6 A3 AR upper is hard coat anodized black for durability. Featuring M4 feed ramp cuts, these upper upper receivers are made for us right here in the USA.Bolt Carrier Group: For AR15 and M16 rifles and carbines. Bolt is made of shot-peened, Mil-spec Carpenter 158A(R) steel. Gas key is secured with grade 8 fasteners and staked. Includes Charging Handle.Lower Build Kit: PSA B5 EPT Lower Build Kit, Black