The Colombo COadvance set contains a pressure cylinder with 95 gram CO, a pressure regulator, a 3-in-1 diffusor and all connections which means you can start improving your plant growth immediately with this set. With the pressure regulator, the flow of CO gas to the diffusor can be adjusted. A bubble counter is incorporated in the diffusor, by counting the bubbles released in a specific time frame the amount of CO added can be determined. The diffusor produces very fine bubbles so the gas is well absorbed by the water.