Groove Tubes GT-EL34-RQ R6 Quartet Amplifier Tube Set Russian-made pentode that's standard issue on many UK amps and has great durability Feature a slightly harsher breakup and less high-end clarity than European models, giving them a distinctive combination of classic and modern tonality Classic "British Sound" Hand Tested & Matched in Quartets (a set of 4 tubes) Limited Warranty Included