How to install a thermostatic concealed 1 and 2 ways extension kit?

Thermostatic shower with Superslim metal plate to embed in the wall, without visible screws. Easy installation with level included. Unlike conventional mixers, we do not have to regulate the temperature of the water while we shower, but in less than a second they precisely compensate for changes in pressure and temperature, keeping the water temperature constant throughout the shower. They are equipped with a mechanical distributor with ceramic discs and a temperature limiter system, thanks to which we save energy.