Dial -Fit-System - Simply turn the dial at the back of the helmet and you instantly have a custom fit.Cool-On-Lining - Hi-Tech, soft, fast drying lining pulls moisture away from you head to keep you cool and comfortable while riding. Cool-On-Lining is removable and washable.Ventilation - While safety is at the forefront of all IRH Helmet Designs, close attention has been paid to the comfort and style of each helmet. IRH front vent design geometry has proven for many years on the market to be extremely effective in allowing fresh air to enter through the front and circulate over the top of your head creating a cooling of your head. ASTM F1163-15