I was having issues with weak cardboard filament spools rolling smoothly on the 8mm rods in my new PolyBox 2.

I tried resizing several existing roller designs, but none fit properly. I decided it was time to learn a little “Fusion 360”. (Fairly steep learning curve for a novice.)

Here is an 18 mm shaft that reduces roll resistance. I would have liked a larger diameter, but that would require cutting the PolyBox dividers.

I borrowed the axle-pin idea from AngryHulk’s excellent spool holder https://www.thingiverse.com/thing:6532008/files.

Assembly: Just push the axle pins all the way into the roller, press the original bearings on flush with the axle end, and drop it in