Perfect for joggers, cyclists, walkers, mail carriers, etc., this unit repels unwanted dogs by emitting ultrasonic sounds at your control. It is also a great training tool. 2-button operation allows you to choose ultrasonic or audible/alarm functionality Convenient flashlight is also built into this unit Range up to 16 yards (48 feet) Weight of only 3.77 ounces Takes 1 user-replaceable 9-Volt CLR61 battery (not included, but available separately).