Griffin Armament MRE Maratime Reciever Ext. AR15. 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. Specifications for Griffin Armament Griffin Maritime Receiver Extension: Manufacturer: Griffin Armament Condition: New Package Contents: Griffin Armament Griffin Maritime Receiver Extension Griffin Armament GAMRE: MRE Maratime Reciever Ext. AR15