Bern 2016 Men's FL-1 Summer Bike Helmet Head Size: 52-55.5 cm In addition, Bern worked with fit-category leader, Boa, to develop the Bern Yoke: a proprietary, lightweight and breathable 360-degree adjustable fit system responsible for near-perfect fit, amplifying the FL-1s safety measure and incredible comfort. Additional features include a reinforced in-mold EPS construction allowing for the helmets distinct angles, lighter weight  Berns lightest to date 18 total vents without compromising strength, dual exterior polycarbonate shells, interior air flow channels for added ventilation, built-in sunglass storage on the shell exterior and internal anti-microbial comfort padding.