TP-Link Tapo T110 Smart 868MHz Door/Window Sensor, CR2032 batteryWindow/Door Safeguard - Monitors the opening & closing of windows, doors, cabinets, the fridge, or the mailbox in real time.Instant App Notification - Is your parcel locked away? Find out immediately with instant notifications.Smart Action Support - Connect the actions with other smart devices for a welcome return home.Easy Installation - Mount to nearly any surface with included 3M adhesive.Great Compatibility - Just one part of the integrated Tapo ecosystem.