Dual Function: Can be used as a door stop alarm and door stopper, Its high damping rubber bearing can prevent the door sliding and prevent the bad guys into. A protector around you. Can be used in home and travel. Notice: The door stop alarms fit for the gap between the door and the ground be 0.6'' and 1.2''. 3 Level of Sensitivities: High-Medium-Low Sensitivities, which can be adjusted according to your own needs. Loud Alarm: Very loud shrill that would definitely scare someone away with 120db alarm. Weight: 4.5 oz. Powered by 9V Battery: The door stop alarm powered by 9V battery, One piece can be used for a year under normal circumstances. Very practical. (Note: Battery not include) Easy to Use: No installation required, Simply place the alarm behind any inner pull door (home, hotel, etc). very convenient to take with you when travel or stay indoor alone. A really must have around you