Genuine Military grade Siemens C3M tube. Condition is "NOS in the box". We offer the BEST QUALITY C3M on market. C3G's previous generation, fully compatible with C3G. Quite a lot pro prefer C3M still!!  Siemens Military grade Communication amplifier. Great for DIY Audiophile Amp too. Quote from DIY Audio forum. C3g, C3m, C3o, what's the difference? C3g was made after C3m, and C3g has a frame grid and gold pins. Frame grids generally give better quality tubes, though it must be said that the quality of C3m is just as superb, and I make the statement here for C3g and C3m, that there is no better tube available of the same kind. Mar 21, 2023 Great tube for preamp or amplifier driver tube Price for each. We will pair when you bought two.