The BIRKENSTOCK Madrid, a classic model that was first launched as a “gymnastics sandal,” has grown to become an essential fashion item. In their shimmering design, these sandals exude elegance with a touch of extravagance. Available in Birko-Flor, EVA, Natural and Oiled Leather upper. Size N = Narrow. For reference a Birkenstock Size 40 is Size 9 Women or Size 7 Men.