Rack for Pololu wire spools?

Since they have a 22mm hole on one end and 31.5mm on the other end,
I’m not sure if a pipe would work.
Has anybody made one?
I have ideas but rather not re-invent the wheel.

Thanks!

Instead of using a 1x4 for the back (the right in the pic), use 3/4" plywood and have places
for several gauges. I have a friend who has a table saw. That would make cutting the slots
for the plastic separators easy.
Suggestions?

Your design seems fine. From our experience, the tilt caused by the holes in the spools are not an issue that causes problems for a holder. When you finish your wire spool holder, we would love to hear more about it.

Grant