The innovative RAPTOR 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. Once installed" the patented RAPTOR upper receiver system allows you to feed from standard box type AR15/M16 magazines or M27 linked ammunition. Spanning the capability range from the optic ready carbine through a lightweight support rifle. The RAPTOR can be user-configured in seconds without tools to adapt to virtually any mission profile. Utilize their Dual-Feed(R) technology at operator discretion" permitting unprecedented firepower and weapon flexibility. Specifications for FightLite Raptor Belt-Fed Upper, Complete Upper Receiver, 556NATO, 16.25 Threaded Barrel, MLOK Rail, Fits AR-15 Lower Reciever, Anodized Finish, Black: Manufacturer: FightLite Caliber: 5.56x45mm NATO Barrel Length: 16.25 in Finish: Black Color: Black Handle Color: Black Features of FightLite Raptor Belt-Fed Upper, Complete Upper Receiver, 556NATO, 16.25 Threaded Barrel, MLOK Rail, Fits AR-15 Lower Reciever, Anodized Finish, Black: Accepts M27 Linked Ammunition Package Contents: FightLite Raptor Belt-Fed Upper, Complete Upper Receiver, 556NATO, 16.25 Threaded Barrel, MLOK Rail, Fits AR-15 Lower Reciever, Anodized Finish, Black