Tests for: Free Chlorine, pH, Total Alkalinity. Spend more time relaxing not guessing with AquaChek TruTest automated color matching! Improved functions include auto-timer, color-matching controls, and expanded instructions. Follow the new instruction guide, dip a strip, place on the digital test strip reader, and it does the work for you - no color matching! Numerical results displayed along with "low", "ok", and "high" indicators. Can also be used in pools with salt chlorine generators! Tests for 3 important parameters in seconds: Free Chlorine/Bromine, pH, Total Alkalinity.