This Double Sonoff Touch is designed specifically to fit into a typical German double-flush mounting box. It is too large for ordinary light switches and consists of three parts: a built-in container, a tile and a cover.
The container contains the high voltage part of the Sonoff Touch. The tile is clipped onto the container, and then the low voltage part can be connected to the high voltage part. Two containers and two tiles are required.
Finally, clip the cover onto the two tiles, which are screwed into the built-in boxes. The cover is derived from a Jung AS500 design used on regular switches.