4-in-1: A very complete kit to check the quality of your water, whether from the tap, hot tub, home-brewing beer, indoor soil grow, aquarium, hydroponics or a swimming pool. TDS tester and PH tester have small size and low weight as a pen, and convenient for you to take it in your pocket when you go out. Easy of Use: TDS water tester will lock the measure result when you press the "HOLD"button and automatically turn off after several minutes of non-use. PH tester has auto calibration function and you can quickly get readout. High Accuracy: The numbers of the pH meter range from 0.00-14.00 (PH), while the numbers of the digital EC and TDS meters range from 0 to 19990 ppm. PH Resolution is 0.01pH, Accuracy 0.05pH.TDS: 0 - 9990ppm, Conductivity: 0 - 9990us / cm, Accuracy: 2%, reliable and quick readings. Easy Calibration: The pH Tester automatically calibrates at three points (calibration only at 6.86 points: accuracy at 0.1 pH). You don't need any tools; simply remove the protective cover and immerse the pH meter electrode in the solution. Press "ON / OFF" to open the electronic pH meter, stir it slightly and wait a few seconds until the readings are stable.