ULTIMATE "SILENT WHISTLE" No 'silent' dog whistle is truly silent. If it were, no one would 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 MECHANISM. Adjustable through a wide range of frequencies using a screw piston mechanism enabling you to tune it to suit your dog, this is the most versatile silent whistle that can be used with all breeds. A booklet is supplied with each WhistleSTORAGE. Ensure whistle is clean and dry before storage. Store out of direct sunlight. Gold Plated finish is packaged in a Blue Presentation Box. ORIGINAL DESIGN. Designed with special air directors to tightly control the frequency produced and generates over a mile of sound with minimal effort. C. Hudson have conceived that elegant shape inspired by Art Deco. CLEANING INSTRUCTION. Always ensure whistle is clean and free from dirt. Clean with warm water mixed with a small amount of disinfectant. Dry thoroughly with a clean lint free cloth.