Birkenstock Boston Super Grip Clog The Boston clog is a veritable classic that can easily be worn all year round. Thanks to its two components, the sole promotes stability and comfort. It comprises a cushioning midsole made from EVA and a nonslip outsole made from genuine rubber. Fastening:Buckle Material Composition:Leather/Leather+Other Materials/Other MaterialsCare Instructions:N/A Anatomically shaped cork-latex footbed. Upper: natural leather. Footbed lining: suede. Sole: nonslip rubber and EVA sole. One strap with an individually adjustable metal pin buckle; dual-component sole made from EVA and rubber. Made in Germany. Non-Marking Sole.