polypin

   an informal unit of volume for beer and other alcoholic beverages, used mostly in Britain. A polypin of beer comes in a plastic container, often inside a rectangular cardboard box; it holds 32-36 Imperial pints (18.2-20.5 liters) or, in the metric version, exactly 20 liters (5.28 U.S. gallons). The word polypin is actually a registered trademark of Biovision GmbH; it is the name of the polythene plastic used for the lining of the container. The traditional British pin of beer (see above) is exactly 36 pints.