Head refers to the component used to seal the end of a container to isolate the internal and external media, also known as an end cap. The head of a cylindrical descriptor is usually a rotating shell. According to the shape of the head surface, it can be divided into convex, conical, flat, and composite shapes. Convex head refers to a head with a convex outer surface shape, such as a semi spherical, elliptical, disc-shaped, and non folded spherical head. Some gas cylinders use a combination of convex inward bottom heads, which can ensure strength and meet the needs of safe use