HM Digital C1000 1000 ppm TDS/NaCl Meter Calibration Solution, 90ml/3oz - 1000 ppm as NaCl; 1060 as KCl; 1450 as 442; 2000 µSCheck out COM-80 / PH-80 + Solution COMBO (Click Here)
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For optimal performance, re-calibrate your meters periodically or if testing TDS or conductivity levels in wide or different ranges.