A referee whistle like no other! Introducing the NEW Fox 40 Caul! The Caul is Fox 40’s first fingergrip-style whistle designed specifically to encompass a flexible fingergrip. Composed of a strong polycarbonate body with integrated over-mold CMG technology, Fox 40 has combined the pealess whistle and fingergrip together in one continuous design. Dual-chamber pealess technology, combined with years of proprietary research and development, has resulted in a one-of-a-kind all-encompassing whistle and fingergrip. The Fox 40 Caul features a sleek design and highly-durable yet flexible rubber form-fitting fingergrip. Fox 40 has evolved traditional beat pea-style technology in to a pealess-style whistle without compromising the traditional harmonized trill tone. Crisp loud sound and extremely easy to blow. Design: Dual-chamber pealess. Sound Power: 110 dB.