Anyone familiar with this?

The plumber put these (rough ins) in both showers in my house. Well, I tried to install my new shower kit with temp control, but the valve cartridge doesn't match the valve body.

The new kit I got came with a new valve body already loaded with cartridge. Its supposed to be a pressure balance cartridge, and from what I've read on the Multichoice bodies any cartridge should fit.

Well, the new body only has two small holes inside. Each has a seal and spring. But inside the rough-in body there are two larger holes, and a smaller third hole in the middle/top with a small plastic (removable) piece sticking out of it, with a conical screen in it.

I've been googling, and will continue to do so, but though someone might be able to help me out...

 

This is what the new cartridge looks like...

 

that looks like some lady's adult toy...

 

Oh, come on, grow up...













this thing only has two small springs...