Wanna add more desiccant to your PolyDryer Box to keep humidity low for longer, this is a small box that can be filled with desiccant. It goes over the existing spool holder and will fit most, even small hole, spools since it's 50mm diameter. The "cap" need to be glued. Didn't want to make screw / latch / anything since this is a dryer box, when you put your box on top of the polydryer to dry the filament you will dry the desiccant too so no need to be able to open/replace desiccant .. so

1. print both parts
2. fill with desiccant
3. put three drops of super glue on the cap and press the cap in, hold for few seconds for glue to set and you are done

opensource as always, you can get source: https://cad.onshape.com/documents/22a5c8543cb85d3b66927338/w/3ad1e05daff79361b3acd9c4/e/0cc693e13fa5f47ba68c038f?renderMode=0&uiState=682b33dd6c065853344472ee