Schneider Electric Merten inserts MTN352000 is a 230V buzzer insert mechanism . And it is mercury free. And heavy metal free, which takes care of the environment and your health as always. Its matching mounting box can be recessed into the surface of the wall with flush type. The buzzer is made of metal, plastic, making it as resistant as possible. Besides it is halogen free halogen free, which is good for your health. The fixing mode of this device is by screw. System M range is based on 4 different surfaces and materials. With 9 different design variations and over 280 functions, the system can meet any customer demand.