Hyper-light and hyper-ventilated The poly-carbonate shell is co-moulded to a layer of expandable injected foam that absorbs the force of impact. The upper ventilation area is reinforced with metal mesh as protection against the penetration of sharp objects. Fresh air flows through the helmet from the ventilation aperture on the front, speeding up along the aeration channel while absorbing humidity and heat, before exiting at the back aperture: the best ventilation system ever! One size 55-60. One handed RUN SYSTEM size adjustment.