I wanted to use the Bambu refillable spool with some Gratkit I had.

I was going to do the trick of ripping off the sides and sliding over the Bambu spool, but found that the GartKit centre bore is bigger and the spool is not as wide.

I therefore mocked up a spacer to go over the Bambu spool and into the GartKit cardboard spool and pack out the width.

It a tight fit as wanted to make sure everything moved as one so it worked with AMS retractions.