United States customary units mass: tower, apothecaries', troy, avoirdupois, and metric. Of these, the avoirdupois weight is the most common system used in the U.S., although Troy weight is still used to weigh precious metals. Apothecaries weight—once used by pharmacies—has been largely replaced by metric measurements. Tower weight fell out of use in England (due to legal prohibition in 1527) centuries ago, and was never used in the U.S. The imperial system, which is still used for some measures in the United Kingdom and other Commonwealth countries, is based on avoirdupois, with variations from U.S. customary units larger than a pound. The pound avoirdupois,
Hong Kong units of measurement and the inch or "tsun" (). Chinese, Imperial and metric weight units are all used in Hong Kong. The choice of system depends on the type of goods and their origins. Metric is used for all official purposes, for example the Post Office and Road signs. Packaged food weights and volumes may be given using any of the three systems of units. Traditional weights are still "de facto" standard in certain areas. For example, vegetables, meats, and Chinese medicines are usually measured in Chinese units, while some fruits are normally measured using the Imperial system. Precious metals (gold, silver and