A closure head is an element used to seal the ends of a container to isolate the internal and external media, also known as an end cap. The closure heads for cylindrical containers are typically rotationally formed. They can be categorized by the shape of their surface into convex, conical, flat, and composite types. A convex closure head refers to one with an outwardly convex surface, such as hemispherical, elliptical, dish-shaped, and seamless spherical types. Some gas cylinders use a composite bottom closure head with an inward-facing convex shape, which ensures strength while meeting safety requirements for use.