Build a true no-lube rifle and shoot round after round without a single drop of oil required. Thats the revolutionary advantage of RF85 technology found in Anderson Manufacturings mil-spec RF85 AOR 16 Complete Upper. Nano technology injects calcium into the molecular fabric of the metal, reducing friction by up to 85%. Since the technology is inherent to the metal, its permanent and doesnt wear out. The optic-ready, forged build of the upper features a 16 M4 barrel with 1:8 rate-of-twist rifling and A2 flash hider. Includes standard charging handle and manganese phosphate Bolt Carrier Group. Traditional carbine-length A2 hand guard. .750 standard-carbine gas block. Caliber: 5.56 NATO. Type: AR-15 Uppers.