Birkenstock Women's Kalahari Shoes Size 41The Birkenstock Kalahari Outdoor sandal is designed to bring comfort and support to your favorite trail and water based activities. The upper is made from the skin friendly, hard wearing synthetic material Birko Flor. Soft microfiber lining and anatomically shaped cork latex footbed. These off road ready sandals feature a rugged PU outsole for added traction and sturdy hook and loop closures for a secure fit.