Groove Tubes GT-6L6-CHPD-R9 Duet Matched Power Tubes Classic design and the most affordable choice in the GT 6L6 line Very strong, smooth, and linear 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