Just my personal experience: 2 Promag CZ-75 mags I bought did not fit CZ-75B as good as original CZ mags. Promag mag bodies
were indeed very nice and made from a good quality steel, but a couple of thousands bigger then they should be to fit/eject w/o problem, so I was forced to grind them a bit. Followers looked like a complete crap, and springs were too stiff, floor plates were jammed and not actually removable, until I also fixed them. I ended up buying CZ followers and springs, and this CZ/Promag combo works good. USA magazines are known crap, nothing to add here. The best thing to do is to buy original CZ mags and
not to worry about nothing.