Consists of the Neptune Space G.divers Full Face Mask complete with GSM G.divers underwater communication system. The ultrasonic transceiver boasts the autonomy of approximately 30 hours in receiving mode- a range of operation of 200-250 meters (calm sea water)- lightweight and sleek design. It is a powerful- single channel and inexpensive PTT (push to talk) underwater wireless communication unit. The unit automatically activates upon contact with the water and it uses a 9V alkaline battery with a "low battery" alarm which beeps every 30 seconds when the battery is low.