This is a replacement for the corrugated cardboard part of Threebees spools so they work with Bambu Lab's AMS. The replacement spool is designed with a slanted groove to prevent it from coming loose. There's two versions, print the one you like.

Use the .step file to print 2 pieces. Should be printable with any layer height, tested with 0.4 and 0.6 nozzle at 0.20mm layer height and 0.30mm layer height.

How to use: DO ONE SIDE AT A TIME!

1. Rip out the existing cardboard carefully, try not to let the filament come loose otherwise you might get tangled filaments or lose the whole spool. 
2. Tuck the filament end (start of spool) in so it's not hanging in the core part of the hard cardboard core.
3. Carefully push the printed replacement spool. 
4. Repeat for the other side.