WHY does Arai still use fiberglass-based shells?

Fiberglass Shell

Decades of experience, research, testing and comparison have led Arai people to conclude that fiberglass-based construction does the best job of performing a motorcycle-helmet shell's main job - spreading impact energy over the widest area through strength, structural integrity and impact flexibility. Arai's aerospace fiberglass technology is at the heart of all our shell composites.

Plus, some newer shell materials have different properties that don't flex as well, or bond together as well, potentially causing problems. Some of them may stop bullets, or make great lightweight fenders. But that's not a helmet's job.