Mesa Boogie 12AX7A Amplifier Valve is the standard 12ax7 that Mesa Boogie supply with their amplifiers. If you want the original Mesa Boogie authentic tone, this Is the valve to choose. Tested on Mesa Boogie's own test rigs ensuring stability and the guarantee of Mesa Boogie's high standards. No Up-sells like Cryogenic tested, just pure tone that you expect from Un-tampered testing.