A super simple spool holder upgrade for the Ender 3/Ender 3 Pro (or any other printer with the same filament mounting bracket).

No supports or any fasteners required. Instead of printing threads to clamp the part onto the bracket, this one just slots onto the top of the bracket. The tight fit ensures that it is secure.

Print the roller and pin vertically (square end down). The roller is symmetrical.

The only thing you'll need is two 608-RS (or ZZ) bearings such as these.