No 'silent' dog whistle is truly silent. If it were, nothing would be able to hear it! The word 'silent' is written in inverted commas because you can hear it, BUT only just. What your dog hears is really loud and travels up to 1.5km. Adjustable through a wide range of frequencies using a screw piston mechanism enabling you to tune it to suit your own dog, this is the most versatile silent dog whistle that can be used with all breeds. A booklet is supplied with each Acme 535 'Silent' Dog Whistle giving easy instructions on adjusting the whistle and training your dog. It is designed with special air directors to tightly control the frequency produced and generates over a mile of sound with minimal effort. Much of its original elegant shape from the period of Art Deco has been retained having been conceived by Clifford Hudson, son of founder, Joseph. Solid Brass lasts for decades. This is the ultimate 'silent' dog whistle. Gold Plated finish is packaged in a Blue Presentation Box.