Which is cylinder made by inorganic material such as glass, ceramic or crystallitic glass, and two metal covers seal a container. There are two contact heads in container, a stationary head fixed on the end of the stationary conductive pole and a moveable head fixed on the end of the moveable conductive pole.

The moveable conductive pole pass through the center hole of the bellow and the metal cover. The bellow, which is brazed to the middle of the moveable conductive pole on one end and brazed to the metal cover on the other end, is a stretchy part can flex axially as its wavy side. Due to the bellow between moveable conductive pole and the metal cover, vacuum switching tubes can keep vacuum seal when the moveable conductive pole move axially. The stationary and moveable conductive head always in high vacuum, the gas pressure should lower than 1.33*10-3 Pa, normally around 10-4 Pa. Around the contact heads and bellow are shield, the shield around contact heads called main shield and the one around bellow called accessorial shield or bellow shield.