Boa Horse Boot. Replaces horseshoes, protects injury or medical condition. New in the box. Size Four. Industry leader in state-of-the-art protection for your horses hooves. Designed to be used in lieu of horseshoes or if your horse keeps throwing shoes. Designed to be used to protect a hoof condition or injury such as founder, navicular, thrush, lacerations, and deep frog damage. Please see the manufacturers written description above, how to measure your horses hoof and the size chart.