Conductivity standards tested and ISO 17025 certified at 25 °C. Uncertainty of measurement of ± 1%. Directly traceable to N.I.S.T. Temperature dependence data is printed on the label as are lot numbers and expiry dates. Supplied in 500 ml HDPE bottle. 1.3 µS/cm in 250 ml bottle. Calibration values 84, 147, 1413, 12880 µS/cm. Control Values 1.3 - 350000 µS/cm.