" The top-rated pH tester on Amazon now comes with a complete calibration and probe care combo kit, including 3 bottles of 8oz pH calibration solutions (pH 7, 4 & 10), one 4oz 3M KCL storage solution, a probe cleaning brush, and Apera's unique CallBox for organizing all the solutions and efficient use of buffer solutions (help you save the cost on buffers by at least 50%). Performing pH calibration in fresh and clean calibration solutions regularly is critical to the reliable performance of pH meters. As a rule of thumb, we recommend calibrating your pH meter at least once a week. And each batch of calibration solutions should be replaced after 10-15 times of calibration. With Apera's Callbox and 8oz calibration solutions, users can perform up to 150 times of calibration. The probe cleaning brush that comes with the kit can help you easily remove contaminants on the glass bulb sensor without any damage, maximizing the life span of your pH probe. The PH20 Value pH Tester is designed for all kinds of regular water solutions pH test, including hydroponics, pools and spas, water treatment, aquariums, aquaculture, beer brewing, winemaking, cooling towers, etc. Up to 3 points of auto. calibration and 0 to 50˚C Auto temperature compensation (ATC), ±0.1 pH Accuracy with 0 to 14.0 pH measuring range; auto. recognition and auto. indication of stable readings saves you the trouble of guessing when to manually hold measurement. With a clear large screen, it supports dual display of Temp./pH value and indicators of completed calibrations (where L/M/H indicate 3 points of calibrations) and stable readings (with a smiley face). Smart self-diagnosis, warning of out-of-range measurement and incorrect calibrations. IP67 waterproof and dustproof. Up to 2000 hours' continuous operation powered by AAA batteries (with low power warning and Auto power off in 8 min if no operation). 6-Month on the the probe. "