This kit tests for pH using the Octa-Slide 2 Comparator. Covers a wide pH range from 3.0 - 10.5 pH. LaMotte company has been supplying laboratory quality pH indicator tests to professional analysts for more than 100 years; these are the most reliable, economical pH kits available. Simply fill the tube to the mark with the sample water, add several drops of indicator and compare the resulting color against the eight permanent color standards in the comparator. Great kit to choose if the pH of sample water is unknown.