The eufy Security Entry Door Sensor requires an additional eufy Security HomeBase or HomeBase E (HomeBase not included). The eufy Security Door Sensor detects the opening and closing of doors and windows, sends alarm signals, and triggers alarms. It has a strong battery life of 2 years (CR123A battery). Its compact design fits any door and window frame. Once a break-in is detected, a loud alarm signal (100 dB) sounds, and you will be immediately notified. Installation is incredibly easy—just peel off the adhesive and attach the sensor to your door or window. Done. Reliable monitoring for complete peace of mind. Created by the Anker team, known for fantastic quality and innovation. Included in the package are a sensor device, a magnetic mount, mounting screws, a user manual, and hassle-free customer service.