This is a  4x2  6u Gridfinity filament spool holder that uses skateboard bearing spool rollers designed by marsgizmo, and it includes a version with space for an inset hygrometer. 
 

The rollers are recessed so the bins are stackable an can be stored away, and there is space for a label if you are into labeling things even when you know what they are. f3d file included 

Printed in PETG
 

Hygrometer

Bearings