I strongly CONCUR with Eastman. Don't waste time (like I did) trying to get aftermarket mags to work reliablly.
ONE "crossed sword" (or new OEM from CZ USA) mag is worth a bag full of anything else. Especially the "mfg CZ" mags...which I purchased 4 because they were such a good deal.
I tried to get them to work for months, even changing mag follower springs and tweeking the magazine "feed throat" dimensions. Never got more than two or four consecutive feeds. I finally swallowed my pride and threw them in the trash after flatening them with a hammer. I didn't want anyone accidentally finding them in my trash and attempting to use them.
The ammo alone that I wasted would have bought me a couple of the real CZ mags.