The Tube Amp Doctor OEM ECC83 / 12AX7 tube is made under TAD specifications with an excellent quality / price ratio. Since these tubes are of the "STANDARD" category and intended for OEM appliances, the selection process is not as careful as the TAD PREMIUM or HIGHGRADE series, therefore no claims or returns will be accepted for this product. For tubes with guaranteed quality, please choose the model RT008 from the same house. The TAD ECC83 / NN008 is a direct replacement for 12AX7, 12AX7A / WA / WB / WC, ECC83, 7025, SPAX7-A.