Designed to work with the filament rack that comes with Palette 2 (10mm rod) but works just as well separately and generally. When used with the Palette-supplied rack, four fits easily.
You can skip the bearings and it spins easily on a rod (12mm diameter or less) OR You can slip some 10mm ID x 15mm OD x 4mm Width bearings (such as 6700, 6700zz etc.) if you prefer
The only support you might need is inside the step where the bearing will go, but might not need it. The ones I printed came off the printer and threaded together perfectly with zero cleanup and my printer is nothing special.