dcoded
You're not an outsider. I keep mine on for the majority of the flight, as do the other pilots who want to prevent hearing loss.
My company allows any TSO headset. I recently flew with someone who had an A20. The plane had the 2 pin plug, and he needed an adapter for the plug. Bose sent it to him.
FYI Bose is releasing a Proflight series 2 headset this month, which is also TSO approved. Less noise reduction but much smaller than the A20.
Protect your hearing.