The PolyMaker cardboard spools are great except for the friction. These spools were straining my printer and the filament always looked so tight between the spool and extruder.

Some designs use bearings, but this seems like overkill and has the risk of being too easy to spin where the spool will unwind several spins if the printer makes a fast movement.

This design uses small peaks on the inside to reduce the amount of area riding on the spool holder. That, combined with lower friction of plastic on plastic, makes this a simply upgrade for those of us using cardboard spools from PolyMaker.

The overall length from end to end is 89mm, the diameter that goes inside of the spool is 55mm and 84mm in length. I've included the .step file if anyone wants to modify. This was made for my Sovol SV06, but I think it uses a standard Ender style holder so it probably works for many printers.