Multi-function: Except as a pet training tool, it can also prevent you from dog attacks, suitable for training many kinds of dogs, such as pets, police dogs and shepherds, suitable for outdoor work, travel and security night patrol. Note: May not be effective for large dogs and ferocious dogs Ultrasound design: based on the theory that ultrasound, the dog trainer can effectively train your dogs to be obedient and stop some unwanted behaviors, such as barking, digging, chewing and more, they are also harmless to humans and pets Easy to use: first open the battery cover, then put in a 9V battery (not included), the sound is audible only to pets, finally turn on the switch and it can work well, they can also serve as a flashlight if necessary. Note: The effective range of this product is 20 feet Portable and convenient: the size of the device is approx. 12.5 x 4.5 x 2.6 cm (L * W * H), which is portable and handheld, also convenient for you wherever you need, such as jogging or walking,