Tung-Sol Tube Upgrade Kit For Marshall 800 Series 2204, 4010, 4104 Amps EL34B 12AX7 This set includes (2) Matched Tung-Sol EL34B power tubes (2) Tung-Sol 12AX7 preamp tubes (1) "Gain Balanced" Tung-Sol 12AX7 preamp tube (phase inverter) marked with yellow "Balanced Triodes" Sticker