Birkenstock Unisex Shoes Slip On Shoes Black Synthetic & Leather This Version Of The Boston Clog, A Classic Birkenstock Model, Is Made Of Extra Soft And Smooth Suede. The Clog Can Be Adapted To All Feet Thanks To The Integrated Strap And A Sturdy Metal Buckle. The Original Birkenstock Soft Footbed Takes The Comfort Factor Even Higher.