Updated 10/3/2019: Added a version that sits higher above the rail and has a cutout for faster print and less plastic.

Finished building my dry spool filament box based on https://www.thingiverse.com/thing:3065301

Used bigger box that holds 5 spools - https://www.amazon.com/gp/product/B07C882DVV
Humidity meter - https://www.amazon.com/gp/product/B07GNMKYCZ
Silica gel - https://www.amazon.com/gp/product/B07N98ZR69

I poured just enough gel to cover the bottom, easy to recharge in the oven but I had the box up for a few months and it is still not saturated while humidity never goes above 19%

Designed a basic top rail guide/holder and the rod support pieces. Also attached roller grooves that can be printed in TPU for stabilizing compatible spools.

Creality

Ender 3 Pro

No

No

.2

80%

80% infil might be overkill but wanted to be strong.