An additional probe of YINMIK YK-2 pH Meter is included in the package in case the original one is accidentally damaged. With one calibration for the replacement, you can have a brand-new pH tester again. Greatly extend the life of the tester [More Accurate & Faster] With low impedance, YINMIK pH sensor ensures the probe high response rate. Premium temperature sensor makes the temperature compensation (ATC) fast and accurate. Never worry about waiting too long for the correct reading [Meet all Your Needs] Perfectly used for checking pH value of Hydroponics Nutrient Solution, Home Drinking Water, Swimming Pool/ Hot Tub Water, Aquarium/ Fish Tank Water. Monitoring pH on Home Wine/ Beer/ Juice brewing, Aeroponics, Ro System, Aquaculture and so on [Easy Calibration] Supporting 3-point auto calibration, following the instruction manual can easily achieve 4.00, 7.00, 10.01 auto calibration. Don't worry about the calibration solution, you can easily configure up to 500ml of calibration solution for each standard using the calibration powder included in the package.