This is a repost from Improved Bambu Lab Reusable Spool Holder by @Blizzard

There are a lot of adapters and spool holders that I have tried, although this one uses more material than others, it has been the most consistantly reliable for me. This project contains the 2 halves for both the ~81mm non Bambu core, and the ~74mm cardboard core. These are the two I print the most, the smaller works great on the esun cardboard spools I've recently purchaced where other “adapters” are either too big or just spin in the spool.

Note: I was unable to find this on MakerWorld so it could be more easily printed via the cloud slicer. If it is already around by the original author I'll take this one down.