OK Pete, I didn't know that and thanks for the explanation.
On the spline tool I bought they give you the part number and say SD (Sea-Doo) 215 255 and 260) HP which can only mean a 159 mm pump. All I know is that the parts I show in the pictures on post #5 worked for my Sea-Doo 215 HP because I used them to change to a Solas 14/19, 159 mm impeller.