Griffin Armament 7075-T6 Maritime Receiver Extension. A six position, mil-spec dimensioned receiver extension featuring 7 ports to allow excess gas, water, oil, and debris to leave the operating system, reducing pressure and associated danger to both host firearm and shooter, while enhancing reliability. Color Anodized Black Material Aluminum Country of Origin United States of America Compatible With AR-10, LR-308 Product #: 650032