This is an adapter to mount Overture/Polymaker (and likely other brands) cardboard spools on a Bambu spool or one of its many derivatives. The adapter is flexible to make installing and removing the cardboard core an easy process since these cardboard spools have some pretty large tolerances.

Print in PETG or ABS, PLA is possible but not the best option as it will creep (permenently deform) with time. If the print detaches from the build plate during printing, add a brim.

See the photos for the sequence of operation

1. Use a filament clip to attach the end of the filament
2. Remove the side of the cardboard opposite of where you see the end of the filament protruding. This is an easy process. Make sure the spool lay flat on a table. Use one of your hands to hold the center of the spool. Pool one edge of the spool until you feel the cardboard starting to detach. Rotate the spool and repeat the process until you can completely remove the side. Clean the paper that remains around the inner edge of the cardoard cylinder.
3. Use a flush cutter to trim the end of the filament (the autorefill of your AMS, if you have one, will work much better that way)
4. Install the adapter on the side of your Bambu spool (or any derivative) where you have the notch.
5. Align the rounded tab on the adadpater with the notch on the cardboard cylinder. The adapter will deform, that's on purpose. 
6. Push down the half spool until it sit flush with the filament
7. Hold both sides of the spool with your hands so they don't separate… Flip the spool
8. Remove the top side of the cardboard spool (same as in 2)
9. Orient the Bambu spool so the locking tab align. Push it in position (it should seat flush with the filament), wiggle a bit to the right and the left if you don't find the correct position on the first try 
10. Lock the spool by turning it
11. Done