NWOT New Without Tags BIRKENSTOCK Madrid Birko-Flor Sandals Black Size 36 = US Size 5 - Size 5.5 The original BIRKENSTOCK Sandal. A strap, a buckle, and a contoured cork footbed are masterfully combined to create the Madrid. The upper is made from the skin-friendly, hard-wearing synthetic material Birko-Flor®. Anatomically shaped cork-latex footbed Upper: Birko-Flor® Footbed lining: suede Sole: EVA Details: one strap with an individually adjustable metal pin buckle