The API CARBONATE HARDNESS TEST KIT is a must-have for any aquarium. This kit includes one (1) bottle of testing solution, one (1) color card and one (1) glass test tube with cap. The testing solution helps to accurately measure the carbonate hardness in your aquarium and provide you with valuable information about your water quality. The color card provides a convenient way to keep track of your aquarium’s water changes and ensure that they are being made properly. The glass test tube with cap makes it easy to store and dispense the testing solution.