CO2 Regulator/Emitter will allow you to maintain ideal CO2 levels for optimum growth. It features an accurate, easy to adjust CO2 flow meter, a pre-set regulator that never needs adjusting, and a solenoid valve. Each unit also comes with the tubing needed to disperse the CO2 evenly throughout your room by attaching the tubing to the back of an oscillating fan. The flow rate is adjustable from .5 -15 Cubic Feet Per Hour. If you are using this without a digital CO2 controller, you will need to use a timer (The ART-DNe Timer is recommended). REG-2 is a dual tank regulator that runs 2 CO2 tanks at the same time, doubling the time between refills! REG-2 has 2 integrated check valves to control the CO2 flow. Both regulators come with 10 feet of 1/4" vinyl tubing for CO2 disbursement.