Barrel: 16" barrel length chambered in 5.56 NATO, with a 1:7 twist, M4 barrel extension, and a carbine gas system. The A2 profile barrel is finished with a nitride coating. Barrel is finished off with an .750" diameter low-profile gas block, DPMS 13.5" Lightweight Hex 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. 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.