Summary

I have only one Raspberry Pi 3 and I have a few microSD cards for different purposes.
2 for RetroPie
1 for OctoPrint
... etc
Because I switch them every so often I made cases for them in order to avoid mixed them up.

EDIT: I've edited also the tray to be wider than the original because I've noticed that the tray was too loose inside the case and used to fall.