Bell boots are designed to prevent damage to the hoof and heel should your horse overreach during exercise.
Sizing:
Small: 13-14 hands ( Pastern circumference 8", boot height: 4.25", bottom circ. 13")
Medium: 14 - 15 hands ( Pastern circumference 8.5", boot height: 4.25", bottom circ. 13.5")
Medium: 15-16 hands ( Pastern circumference 9", boot height: 4.5", bottom circ. 15")