2X Ultrasonic Silent Dog Whistle Stop Barking Pet Training High Pitch Lanyard

Whistle Color:Silver. Whistle size: 4.6 1.8 2.1cm. Rope color:Black. Rope length: About 42cm. Tip: Use three sharp bursts to indicate a call for help. Use two bursts to answer a call. Do not run through your life so fast that you forget not only where you have been, but also where you are.

eBay