DescriptionFrom Mesa Boogie:Our 12AX7’s provide the maximum level of high gain output and overall tonal quality with unsurpassed consistency and reliability. They possess a smooth and balanced response across the tonal spectrum and are extremely lively, open and expressive.Stock preamp tube for all MESA/Boogie Guitar & Bass Amps, Preamps, Power Amps, V1 & V-Twin Pedals