Birkenstock uses premium quality cork to provide the orthopedic contours feet need for maximum comfort. Cork is a natural, lightweight, resilient, and shock-absorbent material. Cork comes from the bark of cork oak trees that grow in Spain and Portugal. Workers peel cork by hand in a process that is harmless to the trees. After seven years of new growth, each tree is ready for harvest again. The cork used in Birkenstock footwear is completely renew-able.