DESIGN & TECHNOLOGY: Ski and snowboard helmet Zonal Koroyd(R) energy absorption Advanced angled impact MIPS(R) protection Hybrid shell design for durability and lightweight construction Adjustable vents Ultimate integration with Smith goggles for optimal comfort and venting AirEvac(TM) ventilation system integrates with Smith goggles for fog-free lenses VaporFit Snow(TM) dial adjustment system for 27-degree fit XT2(R) antimicrobial lining gives sweat-activated odor control Regulator climate control with one-handed vent adjustment 2 vents Removable Snapfit SL2 ear pands for added warmth Outdoor Tech(TM) audio system compatible 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.