This print evolves old Sunlu “reusable” spool to real reusable spool.
Original spool is too narrow for the filament refil. 

But if you use this extension, you can widen each part of the original spool to standard refill width. That means you will get 2 usefull spools from one useless.

Also includes widener for the center of spool. It is separate, because someone might not be interested in it and save some filament.

This version has only 3 large holes. There are other versions, so pick according to your taste :)