Summary

Thanks for [WalterSKW] for the original draft.

These "cages" rest within the central gap of a filament spool. Some spools have smaller 60mm width holes. Some have larger holes at 80mm width.

The idea is that an hygrometer slots into the end. The cage holds a desiccant pack to dehumidify the filament. Thus assembled, store it all in a ziplock bag for cheap diy filament protection. You may, of course, get more complex.

The rings--housings for the hygrometer--are simply included here as crafty bits for makers. They are different widths but fit the same size hygrometer.

example Hygrometers on Amazon: https://a.co/d/4mPBA6d

Also, my U-Hook pegboard filament holders can be found here:
https://www.thingiverse.com/thing:5223576