▲ 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, it emits piercing ultrasonic tone that dogs hate and make dogs away from people. | ▲ If the item you received is defective, please contact us for a replacement or refund. Thank you!