This series of feedthroughs are small in dimension and not too difficult for machining, which ensures a short production cycle and easy installation. Yet they are not able to stand axial thrust too much, affecting feeding quantity directly. This series of feedthroughs are also sensitive to dusts. Moreover, since there are bearings on the vacuum side for crucible feedthroughs and seed crystal feedthroughs, bearings’ grease may have a certain effects on vacuum degree and cleanliness in vacuum chambers.