I bought these amplifier tubes to replace the original EL34 JJ tubes in my Orange TH100, which had started acting up. So far, I’m very satisfied with the sound – it’s incredibly rich! I’m slightly puzzled by the fact that they’re labeled as "matched," but as an average user, I couldn’t quite figure out where that’s indicated or what it means overall. The amplifier itself and the tubes, it originally came with didn’t have any markings. These new tubes have some codes on them, like A/B/C and D, which might serve as some kind of sequence indication, but in the end, I just plugged them in randomly and hoped for the best.