This Dog Training Stop Barking Deterrent Pitch Supersonic Ultrasonic Sound Obedience Whistle with Key Ring - Black is made of metal and plastic. You can train your dog to follow various commands such as "sit", "down", "come", "stay", "fetch" and teach them each command by using a different whistle patterns (for example: two short whistles to "sit", two long whistle to "come"). This dog training whistle is designed for dog training, the frequency produced isn't of effect on person, but very useful for dogs. It is a best tool for you to train your dogs.