This unit of measurement (also specific density) describes the quotient of two densities as a dimensionless ratio. In viticulture, the weight ratio between the volumetric mass of wine or grape must and the same volumetric mass of water (with density 1.000) is determined at a measuring temperature of 20 °Celsius. In the case of grape must, this is also referred to as must weight. The result is represented with four decimal places with the code "d" (for density) or "d20/20" (20/20 refers to calibration of the measuring instrument and measuring temperature). The value of the relative density is analysed in the wine during the quality wine tests and, in the case of a positive decision, is obligatory for the allocation of the official test number (Germany) and state test number (Austria).