This is the original Birkenstock %u201Cexercise sandal%u201D. The Birkenstock Women's Madrid Waterproof Eva Sandal is designed to exercise the foot and lower leg as you wear it. Your foot will flex and grip the toe bar while walking, thus promoting good circulation, building strength and helping to prevent injury. This new water-friendly version is extremely lightweight and is essential for summer days by the beach or pool!Features:Brand: Birkenstock Upper Material: EVA (ethylene-vinyl-acetate) Sole Material: EVA Footbed: EVA Arch Support: Mild Vegan (non-leather) Waterproof Made in Germany