Hemispherical heads with smaller diameters can be pressed as a whole, but those with larger diameters are difficult to press as a whole due to their greater depth, so they need to be welded together using several trapezoidal spherical petals of the same size and a round spherical panel (spherical crown) at the top center. Compared with other types of heads, hemispherical heads require the smallest thickness under the same conditions of diameter and pressure, and have the smallest surface area and the least material when the head volume is the same. The force is very uniform. However, due to the difficulty in manufacturing, they are generally rarely used in other containers except for pressure vessels with higher pressure and larger diameter.