You are purchasing one set of 3/4" flat flanges in stainless steel. Works well for potable water.
These are pretty much universal to any standard pump such as:
Bell and Gossett, Grunfoss, Liquidus, and Taco (along with many more)
Length- 4 1/8"
Width- 2 3/4"
Bolts on center- aprox 3 3/16"