This spacer goes around the metal spool holder on the Printrbot Play, and makes it easier for a filament spool to spin/turn on the printer.I found that my Printrbot Play had difficulty working with filaments from HH3DPlastics and 3DXTech until I tested those on an external spool holder. I created this one to allow me to use the build in spool holder, and it has worked fine since.