This model enlarges the diameter of the spool holder to that of the ERYONE 1kg Cardboard spools:

• From 29.8mm (original spool holder) to 55.5mm

The aim here was to stop the spool holder snagging with the cardboard, and reduce friction on the holder as the filament gets used, meaning the extruder motor has less work to do with more free flowing filament.

I personally printed at 101% scale with supports - This will vary depending on your printers specific dimensional accuracy. I have a snug fit in the spool itself and around 1.5mm gap with the standard S1 spool holder flanges.

This will fit spools with an inner diameter of:

•  55.6mm

I have found this has improved the smoothness of the spool rotation, especially with a full spool which I found to be rubbing a lot on the standard plastic spool holder against the cardboard.