SPECS: Lightweight In-Mold Construction Fuses the Exterior Shell and EPS Foam for a One-Piece Design Zonal Koroyd Coverage for Energy-Absorbing and Ventilated Impact Protection MIPS Brain Protection System Reduces Rotational Forces Caused by Angled Impacts to the Head Select Colorways Offered Without MIPS System Designed for Ultimate Integration with Smith Goggles for Maximum Comfort and Venting AirEvac Ventilation System Integrates with Smith Goggles for Fog-Free Lenses Adjustable Dial Fit for Easy, On-the-Go Size Adjustment DESIGN & TECHNOLOGY: Regulator Climate Control Allows Easy, One-Handed Vent Adjustment 14 Vents Removable Snapfit SL2 Ear Pads Add Warmth and Audio-Chip Compatible Outdoor Tech Audio System Compatible Built with Solar Power Zero CO2 Emissions FSC Certified Wood Cores SIZING: We recommend you try helmets on before buying. Make sure the helmet fits with a little room when the fit system is loose, and sits low enough to protect your child's forehead without hindering vision. Once you've got the right size, you can adjust the fit. Small: 51-55 cm Asia Fit Small: 55-59cm Medium: 55-59cm Asia Fit Medium: 59-63cm Large: 59-63cm Race Large: 59-61cm Vida Large: 59-61cm Asia Fit Large: 63-67cm Extra Large: 63-67cm Youth One Size: 58-56cm Youth Small: 48-53cm Youth Medium: 53-58cm