Battle Arms Development WORKHORSE, Complete Upper Receiver, 556NATO, 16 Barrel, Fits AR-15, M-Lok Handguard, Anodized Finish, Black, Includes Bad Rack-15 Ambidextrous Charging Handle and AR15/M16 BCG WH-UR16B-Y-15 The WORKHORSE complete upper receiver is purpose-built around the forged WORKHORSE 7075-T6 aircraft-grade aluminum receiver and free-float rail handguard with M-LOK attachment point at 3" 6" and 9 o'clock positions. At 12 o'clock is a full-length Picatinny accessory rail with their signature notch cut matching the upper receiver. Every upper receiver is equipped with a 4150 chrome-moly steel black nitride barrel for durability and accuracy. The barrel is individually head-spaced with a matching 9310 steel bolt and 8620 black nitride carrier for ultimate reliability and ease of cleaning.