While other models of the Fox 40 whistles have been adapted to a fingergrip style, the Caul is the first model designed purely as a fingergrip whistle. Made of a strong polycarbonate body with an integrated cushioned mouth grip. Fox 40 has combined the pealess whistle and fingergrip together in one continuous design. Dual-chamber pealess technology delivers up to 110db of sound. A one-of-a-kind, whistle and fingergrip. Features a sleek design and highly-durable yet flexible rubber form-fitting fingergrip. The Fox 40 Caul delivers a crisp loud sound.