Purpose-built for the street. A new benchmark in comfort, quiet, stability and ventilation. Arai applied the same tireless 24-7 focus devoted to our race helmets to designing it, refining and adapting proven concepts to a new purpose. On the rounder end of the head shape spectrum, the Quantum series has always been the "go-to" helmet of choice. The new Quantum-X brings that shape back in a feature rich package.