Comtac style design headset, note that this model does not come with the PTT (push to talk) module. This model needs a PTT module to interface with a radio otherwise it functions purely as an audio in / out headset with a 4-connector pin.
Functions normally as is, add a AAA battery (not included) to run the booster system. Integrated microphones in the head set acquire outside sound to add to your earpieces so you can hear through the heavy padding. Also functions to boost incoming sound to augment your hearing somewhat via the sound level control buttons.