The Moose Horn™ is an open-reed style call that is 100% FREEZEPROOF. The Moose Horn™ reproduces the mating call of an Estrus™ cow. - Open-reed style is 100% FREEZEPROOF - Unique “hose in horn” design automatically reproduces the deep guttural moans of rutting cows in Estrus™ - Includes instructional CD explaining how to reproduce Estrus™ moans and how to use your voice to imitate the grunts of bulls - U.S. Patent No. 5910039