Thermionics means "advanced listening" emblem featuring our KT66 vacuum tube illustration. 3" die cut vinyl sticker. KT66 tube THERMIONICS sticker$3.00PriceQuantity*Add to CartBuy NowWhat you getThermionics means Advanced Listening emblem featuring our KT66 tube illustration. 3" die cut vinyl sticker. Also available with EL84 or 12AX7.