This series of feedthroughs developed for single crystal furnaces are a little bit large in dimension, which are difficult for machining and require high machining accuracy. They run smoothly. By adopting thrust bearings in pairs, the feedthroughs can endure axial thrust of 500kg or so, thus more feeding quantity can be injected, suitable for producing 12〞Monocrystalline silicon. Moreover, since there is no bearing on the vacuum side for crucible feedthroughs and seed crystal feedthroughs, vacuum degree and cleanliness in vacuum chambers can be guaranteed.