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