This is a wall plate for mounting the NA version of the Sonoff NSPanel in a North American dual-gang/double-gang/two-gang wall box horizontally.
The NSPanel doesn't fit properly in smaller single gang boxes, and if mounted in a dual gang box vertically you would also likely have issues lining it up and would also have a huge gap where the other switch should be!
This works for mounting it centered horizontally in the box.

All that's extra that is needed is two M4 nuts to hold the NSPanel backplate against the wallplate using the provided screws from the NSPanel and four screws from whatever wallplate/switches you presumably had there already.