Tung-Sol Tube Upgrade Kit For B-52 AT-100 Amps 6L6GCSTR/12AX7/12AT7 This set includes (4) Matched Tung-Sol 6L6GCSTR power tubes (5) Tung-Sol 12AX7 preamp tubes (1) "Gain Balanced" Tung-Sol 12AX7 preamp tube (phase inverter) marked with yellow "Balanced Triodes" Sticker (1) Tung-Sol 12AT7W preamp tube