Customers no longer need to guess when to change the filters on their RO water treatment systems. The In-Line TDS Meter will give them accurate readings of TDS on the tap water coming in or the purified water going out of their system at any time. The microprocessor-controlled electrodes give accurate readings (+/- 2 %) between 0 and 9990 ppm. All meters come factory calibrated and can be recalibrated with a mini-screwdriver if necessary. The in and out probes are housed in John Guest Quick-Connect 1/4” T-fittings on 24 1/2” cables for easy installation and auto-off function will help to prolong life of included batteries.