Mable Audio is legit. Craig and I get Chinese Pissvane tubes from Mable rather than from the sole NA distributor Grant Fidelity who upcharges a million dollars, but justifies this by describing their test methods using an Amplitrex, yet at the same time being quite nebulous about their grading process: All tubes that went through the Amplitrex test are then further graded according to the 5-spec test results to either A, B or Clearance grade. Top quality grade A matching will be well within 10% – in many cases less than 5%. This is usually a much closer matching than the factory matching method and all tubes with inferior specs on other parameters will be screened off. As many of you know, I have the Amplitrex tube tester. I have several problems with the above statement from Grant Fidelity: We have no idea if these tests are fixed or auto-bias - auto-bias tends to produce results which are more similar and arguably not as a good an indicator of tube state as fixed-bias. Even if fixed-bias, I don't think I've ever seen a new tube be off more than 10% in terms of gain or emissions. Even two different brand vintage tubes of the same type, if they have about the same amount of use, will rarely be more then 10% apart if they are low-gain power tubes. Other specs, such as the Gas or H-K leakage are rarely a factor. I'm still not exactly sure what they match. Do they match so a nominal spec or tubes to each other or on the triodes if dual? As far as I am concerned, any new tube measuring below 10% of the nominal spec for emissions is defective, knowing that most new production tubes seem to measure lower than even slightly used vintage tubes. Again, I haven't seen this myself. As far as gain, a percentage of high-gain small signal tubes will have triodes which differ significantly in terms of gain (more precisely GM). These two sides should be matched as much as possible. If two such tubes are required, then all four triodes should be close. Bottom line: I'm not giving Grant Fidelity the benefit of the doubt with their "testing" to pay them almost two times as much as Mable. If they do test, they better provide fixed-bias results for their high-gain small signal tubes to show that they match (I don't see a matching option during checkout). Too much bullshit - taking advantage of audiophile buyers who already tend to be neurotic.