I was looking for a simple filament storage rack and liked this one by @jimmit, but rather than using a wooden dowel as the original used, I wanted to use some leftover aluminim closet rods I had. Since they were smaller than the dowel rods used in the original, I made some adapters that slide into the original brackets with end caps to cover the exposed bar ends. 

If you still want to use the wooden dowel and do not need the spacer, I also included some caps that can be placed in the brackets to give this more of a finished look.