The Madrid - narrow fit The Madrid is Birkenstock's original sandal. Featuring the classic Birkenstock footbed with the traditional, adjustable single strap for a custom fit and comes in a variety of colours and materials. A waterproof alternative to the Classic Birkenstock Madrid. Great for the beach or beside the pool. This style must not be left in direct sunlight and this material is not designed to be worn day in day out, the classic cork footbed is better for long periods of time or lengthy walks. This EVA style is manufactured in Narrow only from sizes 36-41. Premium Materials Every pair of Birkenstocks is made from the highest quality materials. EVA Upper / EVA EVA - Ethyl Vinyl Acetate is a non-toxic synthetic compound. Creates lightweight and flexible footwear that is shock absorbent. Also resistant to water, oil, and grease. It can shrink at high temperatures. Made from Ethylene-vinyl acetate, this footbed is lightweight and flexible and still offers contours and arch support while being completely waterproof.