They are suitable for ECC81, ECC82, ECC83, ECC85, ECC88, ECC801S, ECC802S, ECC803S, 6BQ5, 6922, 12AX7, 12AT7, E88CC, E188CC, EL84, EL86, PL84, EZ81, EZ80, EC900, PC900, 6HM5, EF95, EF92 and many other types.
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