About This Item :Compatible with Built-in Zigbee Hub: A built-in Zigbee hub is required to use the Zigbee Door Sensor. Please note that the hub is sold separately.(Not all Amazon Echos have a Zigbee hub built-in, but for those that do, it gives you the freedom to create a more local-focused smart home.) Smart Home Automation: The Zigbee Door Sensors can automatically control other Zigbee-enabled accessories through routines, such as Home Assistant, Hubitat, or Alexa Echo Devices--which include the Echo 4th generation, Echo Plus 1st and 2nd generation, Echo Show 10 2nd and 3rd generation, Echo Studio, Eero 6, and Eero Pro 6. Get Notified & Double-check on the Spot: Get immediate app notifications on your smartphone for door and window open/closed with smart Contact Sensors. uses voice commands to see the doors and windows' current open/closed state at a glance, and controls the routines/scenes for peace of mind. Hassle-free Setup: The Mini-sized Smart Contact Sensor is easy to install anywhere without tools and can be detected by Alexa Echo devices with the command "Alexa, discover devices". Package Includes:(By your Choose) 3x Zigbee Window Door Sensors Or 2x Zigbee Window Door Sensors Or 1x Zigbee Window Door Sensors Or 4x Zigbee Window Door Sensors