Transmitting tube GMI-30 (ГМИ-30), pulse triode made by Svetlana. Equivalent of the american 6C21- there are small differencies, but the tubes are normally replaceable. Height of the tube is approximately 33 cm. Diameter of the tube is approximately 13 cm. Weight: approximately 500 g. New old stock tubes. Year of production of all available pieces: 1979.