Birkenstock has always been known for comfort, with their anatomically shaped cork-latex footbed which wears in and gets comfortbale to the point it is hard to take them off at the end of summer. The hard cork footbed has a raised arch to help with problem feet. the upper is made with Birkenstocks own Birko-Flor which is made of easy-to-care-for and hygienic PVC, which has been lined on the inside with a soft, breathable layer of fleece. This style has the added strap at the back for people who are reluctant about the flip flop feel of a mule.