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. Mil-spec hardcoat anodized. 7075-T6 is twice as strong as 6061-T6. Don't put a weak 6061 receiver extension of dubious origin in your defensive firearm. The life you save might be your own.