The OOFOS Ooriginal Black Recovery Sandals Thong Flip Flops are designed for men's size 11 and women's size 13. They are slip-on sandals made of synthetic materials, including the lining, upper, and insole. The outsole is also synthetic. These sandals are perfect for travel and casual occasions during the summer, fall, and spring seasons. They are designed to provide comfort and support for the feet, making them ideal for recovery after exercise or long periods of standing.