Definition: Supplementary units
Supplementary units are units other than net mass, for example, litres, number of parts or square metres. They have to be indicated for certain goods where they are useful measures for the goods concerned. The appropriate supplementary unit is given, where relevant, against headings in the published version of the Combined Nomenclature.
There can of course be differences of scale between the units collected and forwarded to Eurostat and those appearing in the publications (for example, hectolitre is used instead of litre).
Eurostat, "Statistics on the trading of goods - User guide", Office for Official Publications of the European Communities, Luxembourg, 1998, p. 31