The commodity structure of external trade flows of goods is analysed using various internationally adopted commodity classifications which have different levels of detail and are based on different classification criteria. The complex nature of the basic customs and statistical needs makes it necessary to have a rather detailed commodity classification. The Harmonised Commodity Description and Coding System (Harmonised System, or HS), or extended versions based on HS, such as the Combined Nomenclature used by European Union countries, provide such details. Classification using these nomenclatures is based on the nature of the commodity.