drop checker is by far the most reliable way to have a visual representation of your CO2 levels without all the guesswork. This is the simplest and most direct way. When the solution is blue, you need more CO2. If the color is yellow, the CO2 is excessive, if the color is green, the amount of CO2 is suitable! Features: THE PACKAGE INCLUDE:drop checker and 15ML solution PH indicator, the drop checker with a suction cup, it can adsorb on the fish tank firmly and not easy to fall. GOOD CO2 DETECTION TOOL:Color change to determine how much CO2 needs to be added to the aquarium to help novices determine the right amount of CO2 dosage. 3 COLOR DISPLAY:Long term monitor CO2 chroma, the test solution color show: blue - insufficient CO2, green - sufficient CO2, yellow - excess CO2. ENSURE PLANT AND FISH SAFETY:Monitoring CO2 levels in your planted aquarium is very important for the health of your plants and fish. WORRY FREE WARRANTY:Any problem, please contact our store without hesitation. Honor to serve you! Specification: Name: CO2 drop checker kit CO2 drop checker color: Transparent CO2 drop checker material: High borosilicate Size: drop checker: Bottom diameter: 25mm, height: 42mm CO2 indicator solution capacity: 15ML Package Information: Package size: 11.5*11.5*4cm Package weight: 57g Gift Box Packaging(with pearl cotton) Note: There could be a few deviation due to manual measurement or slightly color difference as the result of shooting scene. Package List: 1* drop checker 1* Suction cup for drop checker 1* 15ML solution PH indicator