The Adjustment of helmet has always been ignored or required human being to adjust helmet itself.
Normally there are two kinds of head shape, one is mainly for the white race from Europe and USA, the cranial feature is with narrow cheeks and protruding rear head. Therefore helmets will always designed according to this shape of headform; the other one is mainly for the yellow race with cranial feature in width cheeks and flat rear head, especially for some children in Northern China has the habit of sleep back during their babyhood, it makes the children with the flat rear head and width cheeks. In this case most of helmets did not suitable for Asian populations, since this kind of problem will frequently appeared: cycling helmets could fit the both sides of head, while overall is too big, but it can make the adjustment by rear fit system; Full face helmet has the troublesome since even if front and back is appropriate, but the whole head could not pass the narrow port, only could choose the larger one with adding inner padding to fit the helmet, consequently reduce its safety and comfort.