STOP BARKING : Even if your dog is not in your field of vision, it can accurately transmit the loud ultrasound to the dog you love, he will quickly receive instructions from the owner, and the communication is more convenient and faster, silent without yelling. . For Recall Training : Can be used to recall dogs, train them various tricks, fetching, laying down sitting and so on, and correct bad behaviors. . Adjustable Frequency and Lock : Adjustable frequency can be adapted to the command requirements of different dogs, and different frequencies can also be used to train dogs to make different actions. Long-term and the same tone whistle can make the dog better adapt and receive the signal from its owner. . With 49cm Lanyard : Can be hung around the neck for easy use, compact and easy to carry. . 3PCS : 3 colors ( black,blue,red ) can be shared with family members, and can also be used for behavior training of different dogs. .