Commuter helmet that pulls its weight in traffic. Low-profile urban shape, a built-in rechargeable tail light so drivers see you from behind, and a dial-fit system that locks in once and stays put. Made for the daily ride to work, around town, and back. Integrated rechargeable rear light: Three modes, USB charged, ~6 hours of runtime Dial-fit adjustment: One turn dials in a snug, no-wobble fit. Low-profile commuter shape: Built-in visor, clean lines Fit & Sizing: Measure the circumference of your head about one inch above your eyebrows. Medium: 55-58 cm Large: 59-61cm Weight: 320g (Large)