The laboratory of Liquid Flow maintains two primary flow facilities working in the range from 2.5 l/h to 100000 l/h. The realization of the unit of flow is based on the gravimetric and volumetric principle, respectively. Calibration services for all common flow metering devices are provided using water and MIL-C-7024 as calibration fluids. The measurement uncertainty of the two primary flow facilities is better than 0.2%.