Acme Dog Whistle 535 - Silent Acme Dog Whistle 535 - Silent Adjustable frequency range tuned to your pet's hearing Silent Dog Whistle Ultra High Tone - approx. 3" long and 1/4" diameter Effective up to 2 miles (3 Km) subject to weather conditions and abilities of dog and trainer The picture shows the whistle on one end of the chain and the whistle cover on the other end