FightLite Mission Configurable Rifle Dual-Feed Upper Receiver Assembly, 556NATO, 12.5 Quick-Change Barrel, Threaded 1/2X28, Fits AR-15 Lower Receiver, M-LOK Handguard, Adjustable Sight Set, Manganese Phosphate Finish, Black, Includes Buffer, Spacer, Bolt Catch, Adapter and Compensator MCR-060MS FightLite's groundbreaking MCR (Mission Configurable Rifle) belt-fed upper receiver assembly is designed to interchange with standard AR/M4 type uppers and readily fits any MIL-Spec lower receiver without permanent modification to the host lower, and is rearward compatible to AR15/M16 models produced as early as 1963.