I have 3 or 4 of the Thermold mags. Run them in both my M-14 and my Mini-14. They have worked well for me. They are pinned through the body, because that's what holds the spring assemly in place. They have a 5 round spring, not a full length one, and this is held by the pin. You can remove the base plate, but it's just empty space. I haven't figured out how to remove the spring and follower if you wanted to clean it.