Genuine replacement microphone for various David Clark headsets.  The Model M-7A is an Electret, noise-cancelling microphone designed to operate in place of carbon and amplified dynamic microphones.  Provides clear, crisp voice transmission.  It will not operate in circuits that do not supply a DC bias voltage.  Most modern aviation communications equipment do supply this required voltage.  If unsure, consult with your radio technical manual or with your local avionics shop.  Very simple to replace, includes instructions, hardware and tools.   Made in the USA  823