What the frame size on a spa pump mean?

The frame size on a spa pump is the physical size of the spa pump motor. The frame is the piece that mounts the wet end to the motor. The frame size is located on the motor’s ID plate, usually marked with an F for frame size. The thru-bolt spacing is also an indicator of frame size. A 48 frame motor has bolts spaced less than 4 inches apart, and the 56 frame motor has bolts with spacing more than 4 inches apart.

Diffusers

You may only need to replace part of your jet. Diffusers are exact. It must match perfectly. There are several types and sizes. Here is an example of one. 218-4000 Poly Roto Storm Jet http://www.waterwayparts.com