This ER20 holder fits both - just the nut, just the collet, or both put together.
I also included the FreeCAD source files, so you can edit them on your own without any proprietary software. Please share the models if you make your own.
The trays are NOT stackable. (You may put them on top, but not at the bottom.)
They also do not have places for magnets - putting collets near magnets would be a bad idea, because it would make the collets attract metal chips.
If you are in the EU and want to support my work, I can also print and send these models to you. Please contact me for an offer in that case. Or you can support me by buying something from my shop.
The author marked this model as their own original creation.