Price is for a Matched Pair.  The all new TAD-EL84-STR REDBASE brings together the best of both worlds - the famous EL84-Cz and the EL84M. We opted for the thickest glass possible and the heaviest construction available, just like the Russian EL84M. We combined these features with the most sonically promising cathode plate options in order to meet and exceed the tonal quality of the EL84-Cz, especially with regard to its linearity over the entire frequency range. Finally, we added gold grid wire in order to improve overall reliability. The sound can be described as very harmonic in the mids and treble frequencies, without adding too much power to the bass. The result is the best EL84 in current production. NOTE:   Due to its diameter of 22.5mm, the TAD EL84-STR does not fit into older Marshall DSL401 made till week #20 in 2014 and UK made VOX AC15 TBX amplifiers of the same time range. The tube which did fit these amps is the Ei EL84 or certain NOS models. All new productions of EL84 do use the 22.5mm standard. Later versions of these amplifiers have been updated to accept 22.5mm diameter tubes with no problem.   All power tubes labeled Premium Selected have passed the following tests: -      Plate Current (PC) and Amplification (TC) -      Low Noise Test -      Microphonic Test -      Sonic Tests -      Shock Tests -      Listening Tests -      Shorts & Leakage Tests