Ultrasonic Design: Based on the ultrasonic theory, the dog trainer can effectively train your dog to be obedient and stop some undesired behaviors such as barking, digging, chewing, etc. EASY TO OPERATE: First open the battery cover, then put in 1 9V battery (not included), only pets can hear the sound, and finally turn on the switch to work normally, and can also be used as a flashlight if necessary. Note: The effective range of this product is 23 feet Handheld and Convenient: The dimensions of the device are approx. 12.5 x 4.5 x 2.9 cm (LWH), portable and handheld, also convenient for you to carry around, such as jogging or walking, cycling, parks, etc. MULTI-FUNCTIONAL: Besides being a pet training tool, it can also protect you from dog attacks, suitable for training many kinds of dogs, such as pets, police dogs and sheepdogs, suitable for outdoor work, travel and night patrol. Note: May not be effective for large dogs and ferocious dogs Package includes: 1pc Ultrasonic Dog Trainer Note: Works for most dogs but sometimes doesn't work for those giant dogs