This is an oldham coupling used for eccentric (or shifting) drive shaft connections such as present at the Moineau pump thingy. but requires less height and space than most eccentric couplings.

I am using this coupling in my own Moineau pump derivative (in progress) but am sure more people would like to use it for other unaligned shaft connections. a schmidt style coupling has the same function and height

The motor end of the shaft is designed for a flattened motor shaft to ensure a good transfer of the torque and rotation speed. for the bottom end no hole or connection type is added so it can be altered to your own demands or part to be moved around.

if you like to see a certain type of connection at the bottom please post and i'll add some of the variety's and demands posted (in .stp or .ipt)