Thin Line Cobra Support Boots The Thin Line Cobras are designed to offer the support of a polo wrap, but the function of boot, making them ideal for everyday arena training or show. The Cobra Boot is lined with the high tech, flexible and soft Thin Line material. These boots provide the impact protection and tendon support needed but are thin and pliable to allow the horses to flex their joints with more ease and comfort. Thin Line vents heat so tendons stay cooler and are infused with USDA approved anti-fungal agents to keep your horse's skin healthy and allow for use on multiple horses. Color: Black or White Size: Small, Medium, Large and X-Large.