Critical tool for fast and accurate ph and chlorine readings; Ideal for keeping your pool or spa within the safe Chlorine and PH ranges; no more guess work; An electro-tester for testing pH and chlorine (Cl2) levels in water for routine monitoring of pH and chlorine levels of swimming pools; spas and different water sources; Recommended Chlorine Level for pool and spa: 2 to 1.7 ppm and 7.2 to 7.8 ph for PH Level for pool and spa; Light weight and easy to carry; keep your pool orspa water safe; comfortable and corriosion free; AII the meters are pre-calibrated. If the device needs calibration, please refer to the calibration steps in the included instruction manual.