Filament Spool Adapter

This slides over the filament spool holder on the Ender 3 (bought in 2019). It keeps the filament spool more centered on the holder and provides a little less friction when the extruder wants plastic. With the spool held only with the stock holder, I found that the filament would tighten up a little. It took some torque to get it rotating and that didn't sit right with me.

I didn't do too much measuring or planning. This part fits my machine (Ender 3) and it fits most of my spools of various brands.