BIRKENSTOCK Madrid Big Buckle: Oiled LeatherA strap, a buckle and a contoured cork footbed are masterfully combined to create the original Birkenstock sandal the Madrid. An iconic slide with amplified buckle accent.?? This best selling style comes in oiled nubuck leather its oily waxed surface makes for a unique color effect and develops a beautiful patina. The oily finish of BIRKENSTOCK natural leather products results in color variation, making each and every pair unique. Anatomically shaped