The hot mod adds an extra gain stage and associated circuitry to make your amp scream with tone, gain, and sustain. It was designed for most marshalls and Fenders, and works in most tube amps. The Hot-Mod just replaces a 12AX7 preamp tube, takes seconds to install, no tools are required, and nothing permanent is done to your amp. It's based upon the proprietary "Kontrolled Klipping" circuit found in the world famous Soldano SLO100 the Hot-Mod will make your amp into a screaming beast. Amazing improvements over even the best of amps.
Just a note to you all. I don't sell these Hot Mod Tubes. eBay is the best source I have found for them. $100.00 to $140.00 USD is about the going rate. Good Luck.