Purpose-built for the street. A new benchmark in comfort, quiet, stability and ventilation. Arai applied the same tireless 24-7 focus devoted to their 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. The Quantum-X has Arai's Round Oval (RO) interior fit shape. Shorter front-to-back and a little wider side-to-side (as compared to Intermediate Oval). VAS System: The Variable Axis System shield mechanism was developed to enhance the shape of the shell, but the easy-to-learn changing mechanism is what most people are raving about. Quick, easy and intuitive. PB-SCLC: