I have four Sheaffer fountain pens: Scripto School, Cartridge Fountain pen, Sagaris, and Prelude. I thought the 52mm cartridges which fit all these pens were all the same but they're not!

The ones that I have are: 1) flat on both ends, 2) recessed on one end with what seems like a plug, and 3) like 2. except also has a sliding ball.

Different cartridges work well with some pens and poorly with others. For example, the cartridge with 2 flat ends works fine in both the
Scripto School and Cartridge Fountain pen. One of the recessed cartridges (I'm not sure which one) doesn't hold well on the pen. It slides off and leaves a terrible mess.

My question is: do these different cartridges serve specific purposes? What is the function of the little ball that slides back and forth in the cartridge with one recessed end?

Are there any other cartridges, especially modern ones?