This is the Suunto Wireless Tank Pressure Transmitter with LED Power Indicator Features: Compatible with all Suunto air-integrated dive computers, including DX, D9tx, D6i, D4i, D9, Vyper Air, and HelO2 Monitor tank pressure and air consumption data wirelessly from dive computer Green LED light indicates active data sending Battery life approx. 2 years (100 dives/year) The Suunto Wireless tank pressure transmitter gives you current tank pressure and remaining air time with just a glance at your wrist. Before your dive, simply pair the transmitter with your dive computer and you&';re good to go. The transmitter&';s handy green LED light lets you know that it&';s on.