Women's Nike Flex 2016 RN Running Shoe FLEXIBILITY DEFINED. Top to bottom the Women's Nike Flex 2016 RN Running Shoe is built to flex. Its onepiece engineered mesh upper, comolded midsole and molded tristar outsole pattern work together for a smooth ride that moves with your stride. Engineered mesh upper supports throughout your stride. Comolded midsole delivers a smooth ride. Tristar outsole design flexes as your run. Flywire cables offer a dynamic, supportive fit through the midfoot. Minimal heel design provides a more natural fit. Heel is rounded for a smooth transition at initial touch down.