this spool holder requires a 40mm rod. well it was designed for it, because I had some laying around. 

the holder reaches far enough to fit large 2.5kg spools with up to 300mm diameter. the bracket mounts perfectly to the legs of a Ikea Lack table or to the wall. but it is still small enough to be printed on the Prusa Mini Heatbed. 

i printed it with PETG and 4 perimeters to make it a little stronger. 10% gyroid infill did the job for me. 

Don't forget to mirror the second one accordingly