This is a rack to support up to five spools of filament in a Sterilite 20QT Gasket Box. All it requires is two pieces of Schedule 40 PVC pipe that you can get at any home improvement store. At my local Home Depot they are $4 for a 10 feet (3 meters) length pipe, so quite inexpensive.

The Sterilite box is almost perfect as is, it has a gasket seal around the lid and is just about the right size to fit on a shelf without being too heavy to lift up and down. The only real problem with it is that the ends taper in at the bottom making it too tight to fit anothing more than four spools side by side. However, if the spools are lifted up by a few inches there is room to fit five spools and still close the lid. This model is designed to put the spools at the maximum height possible and still close the lid, thus giving as much width as possible.

The model is designed to be easier to print that the other spool rack holders I have found on here and other sites, with minimal supports, less filament used and half the print time of the others I have seen.

You will need two lengths of ½" PVC pipe. The outer diameter should be 0.84" (or 21.3mm) which matches the standard “Schedule 40” pipe most commonly found. You need to cut them to between 315mm and 325mm or around 12½ inches.

The Sterilite containers are around $50 for 6 at Amazon (Link). 

Update: I added a second size that supports shorter pieces of pipe.  It will take longer to print but will work with pipe as short as 11" or around 280mm.