4 in 1To check the quality of your water, whether it comes from a tap, a hot tub, a home brew, an indoor floor, an aquarium, hydroponics or a swimming pool. In addition, the PH tester pens are small in size, light in weight and easy to carry when you go out. High AccuracyThe pH meters range from 0.00 to 14.00 (PH). PH resolution is 0.01 pH, accuracy 0.01 pH, blue backlit LCD display for reliable and fast readings. EASY TO CALIBRATIONThe pH tester automatically calibrates in three points). You don't need any tools; Simply remove the protective cap and immerse the pH meter electrode in the solution. Press "ON/OFF" to turn on the electronic pH meter, stir gently and wait a few seconds until the reading stabilizes. EASY TO USE The pH tester has a self-calibration function so you can get a reading quickly. Wide Applications A single calibration powder can be easily stored in a drawer, bag or suitcase for easy portability . It is ideal for testing pH balance in drinking water, aquariums, swimming pools, spas or hydroponics. Note: The data is all measured manually, please allow error of 1-3cm Due to differences in light and display, there may be color differences, please refer to the actual item received.