This mocha-coloured flip flop with two adjustable buckles has been a favourite in the Birkenstock collection for years. The Mayari Mocca is made of Birkoflor, a soft material that reduces the risk of irritation and blisters. The orthopaedic foot bed of Birkenstock is unique. Do you suffer from foot or back problems? With the Birkenstock foot bed you relieve your feet, knees and back and reduce the risk of pain. Birkenstock uses German shoe sizes. Therefore you usually need one size smaller than your regular shoe or sandal size..