Volumetric flasks are available in two different accuracy Classes: Class A and Class B. The two Classes differ in the accuracy of measurement with Class A being the highest accuracy, and Class B is approximately half that of Class A. The volumetric flasks with accuracy Class A have a blue print for clear glass products and a white print for amber versions. Volumetric flasks with a batch number and accuracy Class A are supplied with a batch certificate. This certificate documents the mean value obtained from measuring the batch in question, the standard deviation and the day of issue. The batch certificates can also be retrieved online. The batch number consists of four digits. The first two numbers specify the production year, and the following two numbers specify the batch, e.g.: 18.01.