Quality russian electron tube 6C4P-EV (6Ц4П-EB) is a duodiode with undirectly heated oxide cathode. It is direct replacement for the Chinese 6Z4 tube. It is also very similar to the 6X4, EZ90 and 6Z31 from Tesla, but it has different pinout. As a bonus it is a tube with improved reliability and long service life (not less than 5000 hours). New old stock tubes made in the 70's. Manufacturer: Reflektor, Saratov.