This Dry box spool holder is designed to specificallyfit this cheap cereal box and Hygrometer you can buy on Amazon:
Cereal box: https://www.amazon.it/gp/product/B08JTH2NZJ/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1
Hygrometer: https://www.amazon.it/gp/product/B09WGLXRM5/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I use them to store filament in a dry environment, by placing the following silica beads inside the tank:
Silica: https://www.amazon.it/gp/product/B07VG9W5JX/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1