Barrel: 18" 416R stainless steel barrel, chambered in .223 Wylde, with a 1:7 twist, M4 barrel extension, and a rifle-length gas system. The barrel is finished with with a .750" diameter low-profile gas block, PSA 15" 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. 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 MOE EPT Lower Build Kit, Black Includes: Magpul MBUS Sight Set, Black