Matched pair of vintage 6K4P-V (6К4П-В) tubes from manufacturer NEVZ, Novosibirsk (RU). Tested and measured with the RoeTest V10 tube tester and matched in pairs. Pentodes of enhanced mechanical strength and reliability. 6K4P-V is a direct replacement for the chinese 6K4 (Shuguang) tubes which are commonly used in many chinese made headphone amplifiers and analogue of the european EF93 and 6F31 tubes. New in box, directly from the old reserves. Years of production: 1963 and 1964.