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. The volumetric flasks are labelled with an individual number. This is permanently laser-etched onto the base of the volumetric flask and is entered on the corresponding certificate. The accuracy limits for USP compliant volumetric flasks are stricter than flasks conforming to ISO 1042 and therefore satisfy the requirements of the United States Pharmacopoeia (USP). The volume measured for the corresponding volumetric flask, the measurement uncertainty and the day of issue are documented on this certificate.