Madrid Big BuckleThe Birkenstock Madrid is the oldest member of the family of models, making it a veritable classic. Launched as a gymnastics sandal" half a century ago, this simple single strap model has gone on to become a firm fashion favorite. Slip on style One strap with an individually adjustable metal buckle Anatomically shaped footbed Narrow width Materials Upper: natural leather Lining: smooth leather Outsole: EVA Made in Germany Size Guide Fits true to size.