I keep my hygroscopic filaments in dryboxes.  Which works great, but  creates a problem when I unload the filament and need to rewind it into the box.  

Buffers take up too much space to fit easily into 22L SAMLA boxes.   Then I found Dombi3D's buffer for spools, but it worked with bottom berring feeders.   

I designed mine to fit 200mm (1kg) spools, and 4mm wood rods.  

You can customize it with the link to OnShape, as most of the model is parametric.   Change for your size spool or “rod”.  I just used wooden BBQ squewers. 

Fit's nicely  on medium sized printers (ie Ender3) 

Printed in PLA, infill doesn't matter.