Streetwise Smart Sensor Volumetric Alarm Sounds an alarm before an intruder enters; Detects Changes in Air Pressure; Alarms when a door or window is opened Protects up to 1000 ft.; Compact size is great for home or travel Requires: Two AAA batteries (Not Included) Detects Changes in Air Pressure Alarms When Door or Window has been Opened Protects up to 1000 Square Feet Compact Size Great for Home or Travel Product Dimensions: 1.5 x .75 x 2.5 inches