For the safe use of CO2 it is highly recommended to automate the CO2 system with either a simple time switch or a pH controller. The in-line solenoid Control Valve connects the CO2 system with either of these devices.Please look at our CO2 System Info page for a complete list of products needed for a complete CO2 setupIncludes both a hose barb with lock nut for the in-line connection on the CO2 tubing and a standard 1/8" thread for direct connection to a pressure regulator