Simply an adapter to use Masterspool refills on Bambu spools.

The Masterspool refill rolls are smaller that the reusable Bambu spools.
If you want to use Masterspool refills with your reusable Bambu spools, this is the model for you…

This adapter was designed with Bambu AMS compatibility in mind.
Features:

Mirrored design - just one part, print twice
Notch to prevent slipping on Bambu roll
Holes to secure inner end of the filament
Material reduction - roughly 50g per side
No supports or brims needed
How to use:

Unpack Masterspool (leave zip ties in place)
Find inner end of Masterspool refill and slide refill on first adapter part
Put inner filament end into one of the holes in the adapter (carefull while bending the filament, not to break it)
Slide second adapter part into the Masterspool refill

You should now have the adapter with refill in between and inner filament end secured to one side of the adapter.
If yes, the remaining steps are very similar to inserting a Bambu refill into the Bambu spool, just make sure the two adapter halves don't come apart.

Slide complete adapter including the Masterspool refill onto the first Bambu spool part (the one that comes with the tab)
Slide in the second Bambu spool part and twist-lock the Bambu spool parts together
If everything worked and the Masterspool refill sits securely inside the adapter and the Bambu spool is locked: Cut the zip ties and remove them

Available files: .step, .3mf, .stl