The "cone head" has the same function as the "sealing plate". When the diameter of the steel pipe is small, the "sealing plate" is used. When the diameter of the steel pipe is large, in order to avoid collision between the steel pipes on the same bolt ball, the "cone head" is used. The "cone head" or "sealing plate" and the steel pipe constitute the "rod" of the bolted ball space frame structure. Sometimes the "sealing plate" and "cone head" are collectively referred to as "head".