Electron tube 6F10 from manufacturer TESLA is nowadays rare indirectly heated hf pentode, suitable for use in high frequency and wide band amplifiers. Bulb is made out of glass - black painted. 6F10 Tesla is a direct replacement for the american 6AC7 tubes and the russian 6Ž4 (6Ж4). New old stock tubes, tested on BM215A. Perfect condition. Year of production: 1956 (TY - code).