Yay... just found this great explanation on another thread.
For the standard 75B-based guns, which come in two frame sizes, there are two basic magazine sizes.
1) Magazines for compact 75B-based semi-autos. These comes in 10- and 14-round capacities. These two magazines are the same physical size and either will work in a compact gun. The different capacities are due to changes inside the mags. These are the only mags that will fit flush with the bottom of the compact gun's grip.
2) Magazines for the original/standard full-size 75B-based semi-autos. These mags come in 10-, 15-, and 16-round sizes. These mags are physically longer than the "compact" magazines, but the physical dimensions of the 10, 15, and 16 mags are all the same; the different capacities are due to changes inside the mags.
CZ offers other even-higher capacity 75B magazines for other variants of the 75B full-size guns -- and while all of these magazines will work in a compact 75B-based gun, they will all extend farther out of the grip than a mag designed for a compact model.