Electron tube 6F6M1 (6Ф6M1) is a pentode, which was designed for usage in terminal stages of low-frequency amplifiers. This is the metal base version of the 6F6M1 tube, which is nowadays becoming quite scarce. It is direct replacement for the russian 6F6S (6Ф6C), american 6F6G, but also for the VT66-A and CV1911 tubes, the only difference is in the shape of the bulb. Tubes are unused, tested and in original boxes. Made in the the 50's in the well known NEVZ, Novosibirsk factory.