Reporting question for Vacuum Tube - 12AY7, Triode, Dual

Product:
Vacuum Tube - 12AY7, Triode, Dual

Question:
What is the diameter of the glass envelope on this nos 12AY7 ? I need this tube for an AKG c-28 microphone. I have found that most new 12AY7's are too large in diameter at 23cm to fit inside the mic body. The original GE tube is 21cm in diameter. Thank you.

Answer:
At 21cm you would be looking at a tube with a diameter just over an 8 1/4" and that is too large. These 12AY7's are 13/16" (20mm) in diameter.