Gridfinity 1x1x2 for 5 small and 4 medium sized usb devices. I moved the 5 slot row for small devices closer to the edge to make more room for the 4 devices in the 4 slot row for medium USB devices.

The fit for the USB plug is not snug but not loose either. I have one USB plug that is a bit thicker than the others, that one fits but its a bit tight.

No bottom holes for magnets.