Arai XD4 Black Explore Dual Sport Helmet - Large New exhaust ports added to the top diffuser vents nearly double the airflow while using the same (4) 10mm vent holes in the helmet shell. The ability to increase performance from existing designs is typical of Arai&rsquo;s evolutionary thinking. New shell shape for better aerodynamic stability at higher street speeds, works in concert with the high-flow peak and new side cowl vents. New chin vent with more intake ports. Larger sculpted side cowl vents improve ventilation efficiency as well as helmet stability at higher speeds.