Ultrasonic Dog Bark Control Collar,Stop Barking!Humane! Stop your dog from barking in a Humane way--- No electric shock, harmless to your best friend Unit is triggered by vibration from barking (which means it will not be activated by other dogs barking) Has On/Off button, offers Ultrasonic and audible selections LED indicator shows weather the collar is activated Dimension: 2 1/2 inches (width) X 2 1/2 inches (length) X1/2 inches (thickness)