Carbon light solethe northwave carbon light sole is made of a carbon and fibreglass composite with a stiffness index of 100 and 4 vents for constant airflow this combination of materials offers good stiffness without being too harsh as well as excellent value for a performance level shoe slw 2 closure system maximum precision and usability the side button offers dual functionality press the button for micro metric release or lift the button to instantly undo the shoe completely the ergo