Bern Unlimited Watts EPS Summer Helmet ALL SEASON - Pick the model that best fits your style and customize your helmet with our range of seasonal upgrades. Winter Upgrade Kit Available Separately BIKE LIGHT COMPATIBLE - The Asteroid and Meteoroid fit all new and older Bern helmets with a two-hole mount located in the rear of the shell. Lights Available Separately CRANK FIT - Tried and true proprietary dial adjustment system. Simple and durable. Meets Safety Certification CPSC, EN1077B, EN1078 THIN SHELL - Our tried-and-true technology, ThinShell is the ultimate balance between hard ABS or polycarbonate shell thickness and interior EPS foam thickness. Safe, durable and strong SIZE CHART - Season 17: Small/Medium (54-57 cm), Large/X-Large (57-60.5 cm), XX-Large/XXX-Large (60.5-63.5 cm). Season 18: Small (54-57 cm), Medium (57-60.5 cm), Large (60.5-63.5 cm)