Leslie 122 Tube Set Set contains (2) 12AU7 Electro Harmonix driver and relay control tubes, (2) Sovtek 6550 matched power tubes and a Sovtek 0C3 gas regulator tube Used in Leslie 122, 142 and 222 speaker cabinets Used in Leslie 22H speakers with serial numbers 22750 and higher Used in Leslie 22R units serial numbers 40900 and higher