I have a used magazine extension for a Remington 870 shotgun, not sure if it will fit anything else. I am unsure of the maker, or the capacity. (it came on a gun that I bought). It is metal, comes with the spring, follower and the metal mag tube. It is in great condition. It is 8" in total length, I believe it to be the one that adds 3 rounds. I am interested in trading for a 2 round mag extension for an 870 (need a shorter one), Glock 19 mags, AR parts / tools, whatever....even cash, say $40 shipped to CONUS.