Detects if a window or door is closed in real time, Peel & Stick, Local & Remote Alarm, 2 Years Battery Life, Zigbee, Install the Aqara Door and Window Sensor on your door or window at home to always know if they are opened or closed. Do you often forget to close your doors or windows? Just use your phone to find out, can be used through HomeKit with the Aqara Hub.Dimensions: 41 × 22 × 11 mm Battery: CR2032