For testing chlorine, pH, total alkalinity (buffer) and stabilizer.
Just dip an AquaChek Yellow strip in your pool or spa water for one second, and remove it immediately. You get test results in seconds! To keep your pool at its best, test at each end at least twice a week, and test your spa before each use. It's also a good idea to write down your results each time you test, so you can track changes.