Birkenstock Boston Crosstown Slippers The Boston clog, retooled for everyday adventure. A PU sole is durable and flexible, with a rugged pattern for enhanced traction so you can go off the beaten path if you want to. An oiled leather upper takes on a heritage finish the more you wear it. With a contoured footbed that supports you on the go. Details Contoured cork-latex footbed creates custom support with wear Oiled leather upper develops a unqiue, heritage finish Suede footbed lining helps keep you comfortable PU sole is lightweight, durable & flexible Adjustable strap with metal pin buckle Made in Germany Material Upper material: Oiled leather Oiled leather is one of our favourite types of leather. Its oily waxed surface makes for a unique colour effect and develops a beautiful patina. The oily finish of our natural leather products results in colour variation, making each and every pair unique. Insole: Natural leather Natural leather can be recognized by its untreated surface. BIRKENSTOCK purposely does not treat surface grains and other characteristic features. BIRKENSTOCK uses sturdy leather with a thickness of 2.8 to 3.2 millimeters as upper material. Footbed material: Cork Cork is a sustainable material extracted from the bark layer of the cork oak. This natural product is insulating and offers very good cushioning.