CMMG M4 Receiver Extension Castle Nut - Matte black - High quality components and precise manufacturing make CMMG parts ideal for maintaining and upgrading firearms. The durability, reliability and excellent build quality of these parts will ensure years of service you can count on. - At Sportsman's Warehouse, we live for the thrill of the great outdoors. Whether you're hunting, fishing, camping, backpacking, or shooting, having the right gear is key to making every moment unforgettable. That's why we bring you only the highest quality, trusted brands-because your outdoor experiences deserve the best. From expert advice to quality gear and community events, Sportsman's Warehouse is more than a store-we're your partner on every journey. Come explore with us and experience the difference passion makes.