This box is designed to be as small and simple, as possible, to store spools.
So its size is just 20.5 cm diameter and 7 cm high, to fit most spools, without wasting space.
For other spool sizes, you can easily rescale the model.
Recommendations:

I used PETG because of the small wall thickness of 1mm. (feels absolutely robust even with full spools inside)

The TPU seal is optional, but I would recommend it, just to keep it more airtight.

Also, printing one of the many Desiccant boxes for the center of the spool would make sense.