Dog Whistle Ultrasonic Adjustable Frequency The Sounder Dog whistle allows you to use any command on your dog that you desire Frequencies can be changed to fit your pets responsiveness, simply twist and lock the small screw on the training whistle Humans are capable of hearing ALL Silent Dog Whistles so understand that you will hear the whistle while training but the sound frequency levels can be changed AUTHORITY: Are you tired of your pet being wild and uncontrollable? Has every effort to control your pet been a failure? Look no more the Sounder Pet whistle will enable you to control your pet PERMANENTLY! 100% SATISFACTION GUARANTEED! As a quality pet brand we value every customer and pet. If you have any questions or concerns please feel free to contact us at any time!