Birkenstock Unisex Arizona Essentials EVA Sandals are made from high-quality, odor-neutral EVA. They are designed to be anatomically shaped, ultra lightweight, and flexible. They also have a waterproof design. The deep heel cup provides support for the foot tissue and holds the heel bone in its natural position. The heel mold activates the calf muscles and stabilizes the back of the foot. The longitudinal arch supports surround the tarsal bones. The transverse arch support stabilizes the metatarsal bone. The toe grip keeps the toes loose and spread out in their natural position. The footbed edge is drawn up especially high at the front to protect the toes.