Only after print did I realize just how flexible and well thought this design is. It supports smaller spools with or without the spacer ring. Had some extra PETG-CF, so I didn’t use the Fuzzy skin setting since the filament has a rough texture already. My only modification prior to print was to smooth geometry of the outside of the female part and to add additional pass-thrus for filament on the sides of the core barrel. This will be my go to refillable/adapter spool design. (Printed in Night Gray Creality Hyper PETG-CF.)