"With a in-mold construction, this bike helmet delivers optimal protection and Features 21 vents for maximum air flow, breathable mesh pad to keep the helmet breathable and odor free, and an adjustable dial for a secure and comfortable fit. It is built for performance and designed for comfort and safety during your ride. Features: In-mold PC shell improves strength and reduces weight. EPS foam liner for maximum impact protection and integrity. 21 air vents provide good aerodynamics and keep you cool. Adjustable rotary back dial provides secure, comfortable fit. Inner mesh pad for great breathability and comfort. Two sizes for you to choose: S/M (20.5"" - 22.8""); M/L (22.8"" - 24.4""). Specifications: Material: PC Shell & EPS Foam Vents: 21 Color: Black / Green / White (optional) Size: S/M: 52 - 58cm / 20.5 - 22.8in M/L: 58-62cm / 22.8 - 24.4in Weight: S/M (195g); M/L (225g) Package List: 1 * Bike Helmet"