The Birkenstock Unisex Arizona Essentials EVA Sandals are made from a high-quality, odor-neutral EVA. They are designed to be anatomically shaped, ultra-lightweight, and highly flexible. The sandals are also waterproof and have a deep heel cup that supports the foot tissue and holds the heel bone firmly in place. Additionally, the sandals have heel molding that activates the calf muscles and stabilizes the back of the foot, as well as interior and exterior longitudinal arch supports that surround the tarsal bones. The sandals also have a transverse arch support that stabilizes the metatarsal bone and a toe grip that helps keep the toes spread out in their natural position. Finally, the sandals have a raised footbed edge that protects the toes during the rolling motion of the foot.