And 12 is about the max you can get in the smaller frame cize of the CZ 9/.40 guns.
The guns with larger capacities, like some of the EAA guns, use a larger [.45/10mm] frame to give some extra width and capacity.
You'll have to add the spacer to the bottom of the Mec-Gar/CZ mags, to make them LOOK RIGHT.
You can also get flush-fit 10-round .40 mags, if you want a little more "compactness" in your carry weapon.
A bunch of us use the Pro-Mag CZ-75B .40 mags (10-round) with very good success, in both the .40 and 9mm version. In 9mm, these mags give an extra 3-4 rounds.