The Battle Arms Development Workhorse Upper Receiver is made from high quality materials that will supply long lasting durability. This upper features a Rosco Manufacturing 10.5in 4150V Chrome Moly Vanadium steel barrel, chambered in 5.56 NATO, with a 1:7 twist, M4 barrel extension, and a Carbine length gas system. The barrel is finished with a .750" diameter low-profile gas block, WORKHORSE 9.5in M-Lok Free Float Rail, and an A2 flash hider. The Workhorse series offers an amazing value. FeaturesMade from 7075 - T6 aluminumType III hard coat anodizedMatte black finishM4 Feed Ramp