This is a container for storing silica desiccant beads, which you can then put in the middle of your filament spool and seal in a plastic bag to keep your filament nice and dry. It also has a recess in the bottom for holding a hygrometer so you can see that it is working.

I liked the Tenshe's silica holder design, but like some others I had silica beads as small as 2mm that would slip out of the holes. So I copied his overall design and dimensions and made a version with smaller openings. This was my first 3D design and was very satisfying to make.