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 which are numbered individually, are supplied with an individual certificate. The individual number is permanently laser-etched onto the base of the volumetric flask and is entered on the corresponding certificate. The volume measured for the corresponding volumetric flask, the measurement uncertainty and the day of issue are documented on this certificate. The individual number is a consecutive number and comprises three letters and a four digit number, for example: AAA-0001.