Bob, I believe that is a CMMG "Evolution" mag. These were marketed many years ago, and no longer in production. Good luck finding parts for these mags. They were made in a few different lengths/capacities. I have a few "shorty" ten rounders on hand in my mag "overflow" area, never used them for some reason. Just thought they were cool looking at the time, and had to get a few. You might give CMMG a call and see if they have anything left in the "back"😃 but I wouldn't count on it...

 

I love these mags! And i'm not ashamed to say I've cut some of the "Long Cage" ones down to be flush fit with the magwell
for my SSS Space gun. I sold off the 3 25rd ones I had
If anyone wants to offload some of the shorties, PM me.

 

Thanks, I knew finding parts was a long shot.