Ultrasonic dog whistle for training dogs, with a red case. - Brand: SPRINGER - Model: Dog Whistle - Case: Red plastic case included - Frequency Range: Ultrasonic (40000Hz) Ultrasonic Dog Whistle: This whistle emits a high-frequency sound that is difficult for humans to hear, designed to be audible only to dogs. The SPRENGER dog whistle in the image is ultrasonic, and while it sounds like air escaping to humans, it emits a clear, high-pitched sound (40000Hz) that dogs can hear distinctly. It has a screw and nut to adjust the pitch, allowing you to fix the sound's pitch. When not in use, you can store it in the included cover to prevent dust and debris from entering. By rotating the body and lengthening the threaded part, you can change the pitch. A shorter threaded part produces a higher pitch, which can reach up to 360m depending on ambient noise and wind direction. This item is new, but has been stored for a long time. Please refrain from purchasing if you are concerned about any dirt on the attached instructions or if you are overly sensitive to such details.