Stackable Filament Spool Shelf system

update 09/05/2023: added a 23.6mm ID version following a request, hope it helps !

This is a second iteration on my original design. I designed this simple reversible bracket system to manage my spool addiction (see pictures).

It uses a 20mm (or 18mm diameter wood rod, so it's fairly modular in terms of width, cut to desired size. For 18mm wood rod use the adaptor 18 to 20.
The system is now stackable !!! No guess work or measurement required, just install the next row of spool below the previous one (see picture).
Brackets can be installed up or down, or any combination of the two as long as they are aligned.
Backet is design so the wood rod can slide through. allowing for very wide shelf yet well supported, i.e. with as many bracket as desired per rod.
Once happy with the size, bracket has holes for small screw to hold the two rods in place, making the rack sturdy. Nothing will move !
I added some rod cap for even better flexibility of the system.

Hope it helps !