Arai Oval Sizing Chart
How to choose an Arai Helmet?
First, you need to measure the circumference of your head.
Second, each Arai Model Helmet has a different shape because every rider doesn't have the same head.
The Quantum-X helmet is a round oval shape and it was designed for riders whose heads are slightly wider rather than elongated. The round oval shape was achieved by using an interior headliner that combines thicker front and rear pads with thinner side pads.