This modular stacking system is suitable for spools with filaments of 160mm diameters and more. The pipes between the stands have a diameter of 22 mm. It s cut broom handles that can be bought in supermarkets. The pipes are made of metal and covered with a plastic coating. This surface ensures a solid connection between the pipe and the stand. One pipe with a length of approx. 130 cm can be bought for approx. 1,2 EUR.

Other pipe may be loose in the hole and the structure will not be solid. For a smaller tube (e.g. 20mm) it is possible to create and print a sleeve into the hole. For greater strength of the whole structure, the parts can also be glued together with a suitable glue.
For a larger distance between the uprights than 1.2 m or pipes made of plastic or other fragile material, I recommend putting a next support upright in the middle. If there is such a request, I can quickly model it into an stl file. Likewise, if there is a request for a different pipe diameter or smaller lower legs so that the lower coils are slightly off the floor.
Three tiers of coils with filaments on top of each other should be fine. I haven't tested more floors.