eufy Security Entry Sensor V2 (Addon)OverviewProtect Your Doors and Windows from Break Ins with eufy Security Entry Sensor. Once a window or door is ajar by 1. 5 inch, an alert will be sent to your smartphone, and a powerful siren will go off on the HomeBase (can be disabled). Requires eufy Security HomeBase. Easy InstallationJust peel off the mounting tape and stick or screw the sensor onto the door or window you want to monitor. 2 Year Battery LifeOne CR 123A battery provides