My first Pro-Mag for CZ-75 worked reliably. Unfortunately, the second set of two that I bought did not.
For some bizzarre reason, one of them was missing the area of the magazine that locks the slide back (square cut there) after the last round.
The other one would not allow the trigger to reset after dryfiring.
Both went back to the retailer, which promptly issued me refunds (CDNN - great service!).
For me, the factory 15-round mags from CZ-USA have worked 100% reliably. The factory 10-round mag, which came with the gun did fail to misfeed during the break-in period twice. However, the ammo was questionable (American Ammunition of FL), so I reserve my judgement about that. It has been 100% with other ammo.
From my experiences, I stick to factory 15-round mags for absolute reliability.
Skorzeny