["Vivian Emits a high-pitched sound pulse thats inaudible to the human ear but highly irritating to dogs." Ultrasonic wave reaches up to 125db Effectively stops aggressive barking and threatening dogs. Fits in pocket:Protect yourself while walking cycling jogging skateboarding etc. with this handy device. 100% safe to humans and harmless to dogs :Completely safe and does not harm dogs In normal situation it can be used as a normal flashlight to illuminate at night.]