Expertly crafted from aircraft-grade aluminum, CMMG MK4/AR-15 upper receiver assemblies provide a durable and lightweight foundation for your build. Featuring the pre-installed ZEROED Polymer Dust Cover, this upper receiver omits the forward assist, offering a sleek and streamlined design for those seeking a modern, minimalist aesthetic. Whether you're starting a new AR-15 build or upgrading an existing one, this upper receiver delivers both style and performance.