Peggie might correct me on this, but joker valves all fit a flange on a 1.5" outlet (or reduced to a 1" oulet on some electric heads with built-in macerator), and it's a compression fit (made to squeeze the rubber) between the outlet flange seat and outlet housing. Regardless, joker valves for all are about the same diameter. I've owned heads from ITT-Jabsco, 2 models from Raritan, and one from a European maker you can't buy parts for in the US -- and the jokers on all would be interchangeable. The only difference I have noticed -- some have 4 corners to the flaps and some have two, but even that doesn't seem to matter in how they fit or function.

Seems to me jokers are like O-rings or springs, or flush parts for home toilets. Generic usually works.