2-year Battery Life: one CR-123a Battery provides monitoring for 730 days. Designed for doors and windows Small & Compact Design fits onto any door or window frame. 100-decibel siren: if a forced entry is detected, a siren as loud as a jackhammer will be triggered on homebase, and you’ll be notified instantly on your smartphone. Easy installation Just peel off the mounting tape and stick the sensor onto the door or window you want to monitor. Requires eufy HomeBase to use. (HomeBase not included.