Groove Tubes GT-6L6-SD R2 Duet Slovakian Amplifier Tube Set Slovakian made with high power and a very aggressive-dynamic punchy but sweet tone New design with more power and heavy duty components Originally invented by RCA in 1936, the 6l6 Tube has been used extensively in Fender amplifiers since the 1940's Hand Tested & Matched in Duets (a pair of 2 tubes) Limited Warranty Included