instecho Handheld Dog Repellent, Ultrasonic Infrared Dog Deterrent, Bark Stopper + Good Behavior Dog Training Keep unfriendly dogs away; protect yourself from dangerous dogs while walking, jogging, or bicycling; Stop dog approaching you before it can bite you; A good protector for yourself; Also can be used to train dogs and bring you more fun; Need a 9V carbon battery (not included); Safe, humane and effective dog repeller; Can works with most dogs; Emits piercing ultrasonic tone that dogs hate and make dogs away from people.