Groove Tubes GT-6550-R DUET - Newest entry, power and quality should mean long life. Excellent response, yet it's easier to push into distortion than "A" version, a little harder sounding than "C".
Groove Tubes GT-6550-R DUET (code 55066)
Guitar Amplifier Tube, Highest Power Pentode for Marshall, Hiwatt and GT Amps
£89.24 (inc vat)