This is based on the Fusion FIlaments Refill Spool and the AMS Remix by TheMidnightSmith. I added ribs to the inside of the spool for added rigidity when printing in a more flexible material like ABS (it might be rigid enough without ribs if printed with HIPS). I also added filament end retention holes that were removed from the original in TheMidnightSmith's AMS remix. I changed the fillets on the flat surfaces to chamfers for better printing.