I highly suggest you do some serious research before buying any aftermarket mags for a mini. I sold my mini about 5 years ago but I had terrible luck with anything but factory mags.
I managed to get aftermarket mags to work once I bent the lips of the mag and replaced the springs with wolff springs.
I can't explain why so many of the aftermarket mags are junk, but they are.
To be honest I would suggest just paying the outragous cost of getting a couple of factory 20's or 30's that are pinned. They're very robust and should last forever.