Package:3 x Door Stop Alarm: This is an upgrade door stop than others.It is more durable than others with better quality. | 3 Sensitivity Levels - Low - Medium - High,with an adjustable sensitivity switch on the side. | Very loud shrill that would definitely scare someone away with 120db alarm. Each Weight: 128g | You can use it as common door stopper when turn down the ON/OFF switch,hold door in open position. | No installation required.Each requires one 9vbattery(Not include).Portable and easy way to add peace of mind when traveling or working alone.