Pro-Leaf CO2 ControllerPro Leaf CO2 Controller Get precise CO2 control with a Pro Leaf CO2 Controller. You can adjust the output from 400ppm 2000ppm. To prevent CO2 waste, dosing is restricted to lights on, when plants use CO2. You can use it with bottled CO2 or propane gas. Controls CO2 output (from 400ppm 2000ppm) Use it with bottled CO2 or propane gas Day & night mode 1 year manufacturer's warranty Easy Operation To get started it's pretty much plug and play. Day & Night