Dual Function: When the power is in "on" status, it will make extremely loud 120db alarm to be used as door stop alarm; when the power is in "off" status, it can be used as damping rubber door stopper. 3 Sensitivity Levels: Low - Medium - High, with an adjustable switch on the side. H level is the highest sensitive level to trigger 120db alarm.An easy way to make the intruder run as fast as he can! Portable Design: Light weight, small size, easy to pack and take.You can carry it as a security measure for your trip. Small but very effective! Easy to Use: Powered by 9V battery, no mess cable. One piece can be used for a year under normal circumstances. Simply place the alarm behind door.Battery not included. Additional Security: Place the alarm behind the door that you want to be alerted in home, dormitory, hotel or motel room while you are sleeping.2 Modes & 3 Sensitivity Levels Power On: The door stop alarm in “on” status, when door pressure is applied, it will be triggered while make loud 120 dB alarm. Power Off: The door stop alarm in “off” status, it can be used as common door stopper. Low - Medium - High, with an adjustable sensitivity switch on the side. Portable Design Small size and doesn’t require any wiring or complicated installation making it ideal for bedrooms, apartments and dorms as well as for hotel rooms when traveling. Specification Size: 5.8*1.8*1.5 inch Alarm Level : 120dB Material: Stainless steel cover/Plastic body/Damping rubber bottom Note The gap between of door and floor is from 0.32 inches to 1.35 inches. Smooth floor recommend to use H sensitivity Level with vibration-sensing alarm. If the alarm sound gradually become not loud enough., you need to replace battery. Requires 1x9V battery,not included.