HM Digital C342 TDS and EC Calibration Solution, 342 ppm (NaCl), 90 ml Volume NaCl calibration solution, available in 342 ppm or 1000 ppm Comes in lightweight HDPE plastic bottles Sealed with a coated foam liner Use the HM Digital TDS Calibration Solution (342 PPM) to periodicallyre-calibrate your HM Digital TDS meter or HM Digital Water Quality Tester This HM Digital TDS Calibration Solution is also known asWater Tester SolutionandTDS Meter Calibration Solution The C-342 is NaCl solution (342 PPM)