Wall spool holder is designed by my own for 28mm wooden dowel. Construction is very robust for hold thirteen 1kg filaments in my case. The model is strong enough for a higher weight depending on the material of the wooden dowel. It is recommended to use at least 4 perimeters and a modifier in the screw area for 100% infill. Rest 10% Gyroid. I tested with PETG and the strength looks good. Needed 250mmx250mm heatbed at least. Enjoy it :-)