HJC CL-17 Mission Helmet - X-Large/MC-4F Advanced Polycarbonate Composite Shell - Lightweight, superior fit and comfort using advanced CAD technology Aerodynamic shell shape reduces turbulence Impact absorbing, multi-density EPS liner ACS Advanced Channeling Ventilation System - Full front-to-back airflow flushes heat and humidity up and out DOT FMVSS 218 Certified