Hach AquaChek Dip-and-Read Water Quality Test Strips, Total Hardness, 0 to 425ppm (50-Pack) Simply dip into a sample or hold under a liquid stream; for most products, in one minute or less, results are available to compare with the color chart included on the bottle's label AquaChek multiparameter strips perform five water quality tests at once: Free Chlorine (04ppm), Total Chlorine (010ppm), Total Hardness (0425ppm, 025 gr./gal.), Total Alkalinity (as CaCO3, 0240ppm), pH (6.48.8) Fast, easy, reliable onsite environmental testing