4 in 1 PH tester: A very complete kit to check the quality of your water, from the tap, to recovery, through the aquarium or the swimming pool. TDS / PH testers have small dimensions and light weight as a pen, pH meter for drinking water, beverages, for aquariums, hydroponics, swimming pools. pH meter easy to use Usage: TDS water freezes the measurement result when you press the "HOLD" button and automatically shuts off after a few minutes of non-use. And these 2-in-1 pH meters and TDS meters are also ideal for home testing. High Accuracy: The numbers of the pH meter range from 0.00 to 14.00 (PH), while the numbers EC and TDS digital meters range from 0 to 19,990 ppm. Use digital meter to get precision numbers instead of comparing color with pH test paper, avoid making inaccuracy due to different light, also helpful for low color ones. Easy calibration : The pH tester self-calibrates at three points (6.86 and 4.01 point calibration). You don't need any tools, just dip the pH meter electrode into the solution. Press "ON/OFF" to open the electronic pH meter, shake lightly and wait a few seconds until the readings stabilize. What you will get in the package: 1) A TDS-EC tester with case. 2) One PH tester with hard plastic storage 3) 3* PH calibration pouches. 4Use the instructions.