Electron tube 6F6S (6Ф6С) is a pentode, which was designed for usage in terminal stages of low-frequency amplifiers. This is the older "figural" version of the 6F6S tube, which is nowadays quite scarce. It is direct replacement for the american 6F6G, but also for the VT66-A and CV1911 tubes. New in box tubes. Year of production: 1965. Tested.