No shell helmets are generally the lightest weight.Most come with a nylon cover.It is necessary to keep this cover on for the helmet to work properly.

• 而无外壳的头盔通常比较轻；它由尼龙覆盖；无外壳的头盔一定要保证外部的尼龙材料工作正常(不太明白；涂点东西也能救命吗?).