ACME whistle 210 1/2 and Thunderer 560 trill whistle with lanyard trill This Set consists of ACME whistle 210 1/2 with clear high tone for common commands and of ACME Thunderer 560 trill whistle which is mostly suitable for stop-command. These whistles are extremely durable and their tone is independent from the influence of the weather. Due to the standardized frequency, the desired frequency can be ordered any time. Trill whistle has waterproof ball inside. Delivered with nylon lanyard in colour matching to the whistles.