This series of feedthroughs developed for single crystal furnaces are a little bit large in dimension and require high machining accuracy. They run smoothly. By adopting thrust bearings in pairs, the feedthroughs can endure axial thrust, thus more feeding quantity if appropriate can be injected. 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.