Helmet is a device to protect the head, a hat worn by soldiers in training and fighting, and an indispensable tool in people's traffic. Divided into military helmets, police helmets and civilian helmets. Mostly semi-circular, mainly composed of shell, lining and suspension device. The shell is made of special steel, glass fiber reinforced plastic, reinforced plastic, leather, nylon and other materials, so as to resist the damage of bullets, shrapnel and other hitting objects to the head. In ancient China, it was called Zhou, Shoufu, Tofu or.