The larger capacity Mecgars can be "different."
I bought several for my CZ 85 (Pre B) and my son's CZ75SAO.
I'd used 16 round magazines to test my fitting work to allow me to use modern magazines in my Pre B pistol's frame. No time at all I had them sliding in and dropping out.
So, I went three better (19 round Mecgars). I kept 8, have my youngest so the rest. Loaded them up, set some aside for the CZ75 Compacts and four for the Pre B CZ85. One day I ran into a 19 round magazine that wouldn't fully insert into the Pre B pistol. Then I had to check all of them. Of the eight 19 round magazines, only four would insert smoothly. I emptied the ammo from them and talked to my youngest son. He tried the in his CZ75 SAO and all four worked great. I tried the first batch I'd bought for him and ran across four that would insert smoothly/completely into the Pre B CZ85. All of them are Mecgar 19 round magazines. Some worked in the Pre B (with the frame/mag. well filed to open it up for modern magazines) and some didn't.
I also removed the magazine brake from the Pre B CZ85 way back there. It was sort of bent/twisted and binding even with the 16 round mgazines, so I removed it and never looked back. Now I can see, and lube, the hammer spring and strut any time I have the magazine out.