JBL ProFlora Calibration Set is a complete set with liquids requried for professionally calibrating of pH sensors (electrodes).JBL ProFlora Calibration Set+ 50 ml pH 7.00 buffer solution+ 50 ml pH 4.00 buffer solution+ 50 ml de-ionised water+ 3 cuvettesEasy to use:Fill buffer solutions into cuvettes. Immerse pH electrode in calibration solutions according to instructions and rinse afterwards. pH electrodes need to be readjusted (calibrated) every 30 to max. 60 days. To do this, they are immersed in calibration liquids with a given pH value and the device then readjusts itself. Only 5-10 ml calibration liquid is needed per calibration procedure. Then rinse with distilled water (included in the set)