A warm-weather essential, the Vionic Islander Flip-Flop has a sleek simplicity that makes it the shoe you're sure to pack for your next excursion. Lightweight, flexible medium-density EVA midsole absorbs shock, reducing stress on feet, ankles, and knees. Durable TPR outsole with patterned tread helps improve traction. Recommended by Dr. Andrew Weil. Vionic brand's biomechanical technology is shown to be an effective treatment for heel pain. Vionic brand's biomechanical footbed supports you from the ground up. By building biomechanical technology into premium footwear, Vionic brings together the best of science and style. For the greatest comfort, we recommend wearing your new Vionic footwear for just a few hours for the first few days to allow your feet to adjust to the new level of orthotic comfort and support. Within one to two weeks you should find the product completely comfortable and supportive. Vionic Natural Alignment.