This is simple cap for desiccant container of prusament spool. The original model is “Prusament Hygrometer Desiccant Container” by 4nthonylin. The idea of hygrometer with dessicator is great. It is easy to find refresh time of silica gel. However, I frequently change filaments. This container hold spool hole and I don't need hygrometer for every spools. so I design suitable cap for “Prusament Hygrometer Desiccant Container”.

Please prepare body for desiccant container “filamentbody.stl” from 
https://www.prusaprinters.org/prints/35562-prusament-hygrometer-desiccant-container
 

This desiccant container fit for Prusament spool. You can stock prusament spool with desiccant container. 
Keep filament dry!