Looking for some Thunder! This is the Standard Retube Kit for the Fender Super Bassman and Pro 300. For the front end this kit contains three standard ECC83S's and one current balanced ECC81 for the phase inverter. The default power tubes are a matched sextet of the JJ Electronic KT88's however you can configure this kit to use a sextet of the JJ 6550's by clicking on the "Customize" button!
These amps are adjustable bias and all you need is a Multimeter to adjust the bias using the test points.