I recently bought 3 hi-cap Promag magazines for the CZ-75B from CDNN.
(If you're unfamiliar with CDNN, check out a recent copy of Gun List or Shot Gun News. They also had an ad in Shooting Times this month, featuring the mags in question.)
I've put 500+ rounds through the mags since last month, and they've functioned flawlessly. And, they cost only $14.99. I won't be buying any new CZ hi-cap mags, but I may buy some more Promags.
(I haven't always had this kind of success with after-market mags, but for something as common CZ or S&W, they generally work pretty well. The S&W mags are almost identical, incidentally, with the only obvious difference being the mag release slot position. I have to be careful when I put them away so as to not get them mixed.)
[This message has been edited by Walt Sherrill (edited February 24, 2000).]