Adjustable Frequency 5400-12800Hz. Protective end cap. Designed with special air directors to tightly control the frequency produced and generates over a mile of sound with minimal effort. Quiet human audible sound to confirm the whistle is working. The whistle is engineered to produce a relatively quiet whistle sound audible in the human range the sole purpose of this is to reassure the user that a sound in the required range is being produced Includes information leaflet giving easy instructions. Solid Brass with a Nickel Plated finish. Genuine ACME Whistle made in the UK by specialists with over 150 years of experience.