Code Red Battle Zero M4 Head Set. The lightweight Code Red Battle Zero M4 Communications Headset sports bone conduction technology that transmits and receives audio directly from vocal vibrations in the skull. The speakers on this Communications Headset from Code Red do not block your ears improving situational awareness so that you can hear all around you. For the best way to stay safe on your next scouting or tactical outing choose the Code Red Battle Zero M4 Headset. Package Contents: Code Red Battle Zero M4 Headset Code Red BattleZero-M4: Battle Zero M4 Head Set