The threads on this are not great and hard to thread.

I wanted desiccant holders that I can put in the center of all my spools and leave in my AMS all the time, but also would fit in a cardboard spool adapter / broken spool adapter. This adapter fits spools that are about 63mm and narrower (my kingroon cardboards are too wide, but kingroon plastics fit oddly enough). The desiccant holder fits inside every spool I have tried so far given how small it is.

Note, I printed the desiccant holder in PETG because I dry out the desiccant on my heat bed. The spool holder does not need to be PETG (PLA is fine), but I had PETG loaded and was lazy :)