The Nitrus is another masterpiece made by Montrail. It is flexible, conforming, upper expands to accomodate wider feet. A four density midsole plus TerraHex cushioning and control system along with airmesh windows to enhance airflow. TerraFlex protection along with a stretch gusset keep your feet protected from all the trail will throw at you. The perfect shoe for sensitive feet, high mileage runners and those who want the perfect combination of support and cushioning.