md 600 driver,
The Bose X helicopter model has the option of different impedance microphones (and changeable plugs as well if you're flying French and American helicopters). You simply unscrew one microphone unit and replace it with another. The extra microphones are quite expensive (but cheaper than having 2 headsets). You can get them from places like Sporty's or Marv Golden, though it may take a phone call to make sure you get the 2 microphones. David Clarke just have an impedance switch on their H10-66.