The Colt AR-15 Upper Receiver Assembly with Monolithic Rail comes complete with charging handle, bolt and bolt carrier assembly. Featuring a flat-top upper receiver with picatinny rail, this assembly is more than ready to offer the shooter maximum versatility when it comes to mounting accessory devices. Unique to this upper receiver, is the free float monolithic rail which is machined together in conjunction with the upper receiver portion of the upper assembly. The monolithic rail presents the user with an extremely versatile single plane rail which eliminates the chance of front mounted accessories being canted or unlevel. The Colt Upper Receiver also feature a free-floating barrel which is designed to enhance accuracy and target acquisition. FeaturesMonolithic RailFree-Floating BarrelFlat Top UpperA2 Flash HiderBlack Parkerized FinishFlip-Up Rear Sight