Ruby Tubes EL34CZ-2 Duet Matched JJ EL34 Power Vacuum Replacement Amp Tubes (2 Pack)The EL34CZ 2 Power Vacuum Tubes from Ruby Tubes come as a perfectly matched pair! JJ modified EL34 with great tone and lots of power. Very dependable. Bold bass, thick mid range. Good high end, not too bright. Great for the classic rock n' roll sound. All RUBY Tubes come already Matched with a 6 Month Warranty There is no extra charge for this service. Our Magic Parts matching process is very exact and our tubes are matched within + 1 mA (mille amp)