Character: Generally a helmet is made by foam materials (to absorb the impact of movements in order to protect the head) as well as smooth shell.
Useless: anti-collision, preventing the leaves and branches beat, preventing flying stone beat, separating storm, ventilation, speeding up. The helmets with visor could be sun block, to apply the reflective sticker on helmets will prevent collision when riding at night.
Inner padding: the part to collect the head with inner helmets, it makes us feel more comfortable to wear a helmet as well as provide the buffer function. Well-made helmets are with large coverage, better quality and even more strong collection to attach with inner helmet.
Wearing comfortable: This individual feeling is mainly because whether the weight, inner padding, strap and size range is appropriate or not, to wear a comfortable helmet could reduce the oppression on the head and neck, also could maximize protection effect when impacting.
Permeability: It will make the scalp under harmful effect to let the head under airtight condition for a long time, also will make the riders feel uncomfortable. So a good helmet should be with more holes or large holes, all those are supposed to improve the permeability.