Crown's B-20.3 polycarbonate lenses are three times lighter than glass lenses, and 20 times more impact resistant. So eyes are protected from projectiles and UV Rays. Because Bolle has forged the frame from B88 nylon, it's both light and strong.And the Bolle Crown stays in place with Thermogrip nose pads and temples. Durability is increased with pinless hinges, which replace breakable mechanisms. Lens scratching is reduced with Carbo Glas coating. Bolle Crown sunglasses are designed for medium-sized faces.