Spool rack (remix) for shelf storage

I have lots of mostly full spools, which I prefer to leave on the shelf by my printer. To make getting them out and putting them away easier, I looked for something simple to keep them from rolling around. But as usual, nothing quite worked for me.

Using heinandre's basic design, I sized and crafted this thing to accommodate the largest and smallest spools I have. Each rack holds two 1kg spools, and I think uses as little PLA as I could manage.