This AR15 Upper Receivers from VLTOR is unlike many others. As a modular upper receiver (MUR) it is made to be a rigid, Mil-Spec flat-top upper so that it seamlessly fits with all Mil-Spec AR 15/M4/M16 rifle and carbine lower receivers. Since the MUR is rigid and durable with a thicker wall, it can support larger optics and improve your accuracy, as the recoil is lessened. With various models, you can even customize what you want in an upper receiver. For example, the MUR-1A model has a shell deflector and forward assist, while the MUR-1S has a one-piece machined shell deflector unit for a more streamlined look. All MURs are made from 7075-T6 Aluminum to give you as much durability as possible while still being lightweight enough to handle easily. Specifications for Vltor Modular Upper Receiver: Manufacturer: VLTOR Color: Black Finish: Black Caliber: 5.56x45mm NATO, .223 Remington Gun Model: AR-15 Condition: New Features of Vltor Modular Upper Receiver: Multiple variants lets you customize your upper receiver Made to be Mil-Spec for wide-ranging compatibility V7075-T6 Aluminum for durability and weight reduction Package Contents: Vltor Modular Upper Receiver (MUR) The Vltor Modular Upper Receiver is a quality addition to the VLTOR lineup. For more great deals on AR15 Upper Receivers by VLTOR, please browse our Vltor Gun Parts page. Which weapon models is Vltor Modular Upper Receiver compatible with? Vltor Modular Upper Receiver is compatible with AR-15