This wired doorbell adopts premium ABS shell material, which is flame retardant and anti-flame, you can use it with confidence. This doorbell has a built-in 90dB speaker, which can produce loud sound , you won't miss the ringtone. There is no need to replace or add a battery to this door chime, because it uses the access control power supply, which is environmentally friendly, convenient and easy to use. save money.This doorbell could be wall or double side adhesive glue, very easy to install This wired external doorbell could be used for security access control. It is sturdy and durable for long time service. Note: The data are all manual measurement, please allow 1-3cm error, due to the light and display difference, there will be some color difference, depending on the physical item received.