I have extended the original Prusa i3 Hephestos spool holder with a 32mm installation tube. I use this spacer to hold the filament spools apart, so they can't touch each other while printing.
You can easy create your own spacer with the Customizer. The Customizer creates one STL file for the spacer and one text only file if you want to use dual extrusion. Please don't forget to add some backlash to the inner diameter when customizing, otherwise the spacer will fit to tight!
The spacer on the first image are colored accordingly to the electronic color code.
If you want to print text on the spacer, please note, that you have enough space on this sides. Otherwise leave the text fields empty.
I printed my spacer with 20% infill and 0.3 mm layer thickness.