This test kit features a unique dye that has a pronounced color change between 8.0 and 8.3, making it the easiest kit on the market to read in that critical range. Alkalinity may be read from the same sample in 0.5 meq/L increments. MultiTest Marine pH & Alkalinity performs over 75 tests and contains a reference sample for validation. Range: pH: 7.80–8.70, alkalinity: 0–∞ . Precision: pH: 0.01 pH units, alkalinity: 0.5 meq/L