These are unused old stock with generic tube boxes. The Mesa Boogie MESA 12AX7 is a premium-grade preamplifier tube. It’s designed to provide high gain output with an overall balanced tonal quality. You’ll also find that the MESA 12AX7 is both consistent and reliable in its smooth, balanced tonal response. The MESA 12AX7 is a lively, open, and expressive tube. It has a plate size similar to NOS USA made 12AX7 rather than the very short plates found on many new production tubes.