Package Include: 1 x Double mini Display Valve body 1 x 110v US standard solenoid valve installed on the valve body 1 x Fine-tuning Valve installed on the valve body 1 x Bubble counter with check valve fucntion 1 x installing tools ATTENTION: 1.The maximum working pressure is design at 75psi(56Pa), if your cylinder inner pressure over this value, Solenoid valve will not open, will not working. 2. During the transportation, the core of the Solenoid valve may offset which will cause buzz sound, you can rapid turn on/off the power 5-10 times to fix the problem. 3. If you have fishes in your plant tank, DONT add large doses suddenly, large dose CO2 will affect the PH of the water much, the fishes may be will not fit in.