The Tunze CO2 Valve Set 7070.200 is an electronically controlled solenoid that connects directly to the Tunze SmartController 7000. The solenoid valve plugs into one of the controllers in/out control ports. It comes with a Y adapter cable allowing you to connect another light or pump in-line to the solenoid valve with individual control. The valve can be used for almost all types of gas including CO2 and oxygen making it useful for more than just CO2 reactors.