Dog whistle: this is one of the most useful tools used to bring back a dog. Not only does sound of a tube form dog whistle that humans can hear, but it also produces ultrasonic frequencies that only dogs can hear. This frequency ultrasound is so far away that the dog can hear it in the distance. Ultrasonic wave: ultrasonic energy is large and propagated along the straight line. The ultrasonic waves emitted by the dog whistle can be clearly identified by the dog. The owner can use the dog whistle to blow out different tones to give instructions.Depending on the rhythm of the sound, you can let the dog understand the meaning of each rhythm and the instructions given. About 5cm Long (depending on adjustment) Color: Black, Red, Pink, Orange, White, Blue, Green, Light Green, Silver Lightweight. Package include:1pc Dog Whistle Note: 1> Please allow 1-3cm error due to manual measurement, make sure you do not mind before you bid. 2> The colors may be different for different displays, please understand. How to train your dog? 1. Using a different flute method to specify \"don't move\" \"sit\" \"come\" and so on. For example: \"Don't move\u201d: two short sounds. \u201cSit\u201d: a long sound, a short sound. \u201cCome\": two short sounds. When teaching the dog these movements, play the dog flute according to the regulation, then teach him to do the corresponding action. Train again and again, and your dog will know what to do when he she hear the sound of the dog whistle. 2. The dog's behavior according to your instruction need to be trained. Such as, at meal time, blow on the whistle before they get the food. It will only take a few times of doing this and your dog will react quickly.