Beer stein ( ), or simply stein, is an English neologism for either traditional beer mugs made out of stoneware, or specifically ornamental beer mugs that are usually sold as souvenirs or collectibles. In German, the word means stone and is also used to refer to any beer mug which holds 1 litre (in some parts of Germany (i.e. Bavaria) they use the word 'Maß' instead). Such Steins may be made out of stoneware, pewter, porcelain, or even silver, wood or crystal glass; they may have open tops or hinged pewter lids with a thumb-lever. Steins usually come in sizes of a half litre or a full litre (or comparable historic sizes). Like decorative tankards, they are often decorated in a nostalgic manner, but with allusions to Germany or Bavaria. It is believed by some that the lid was implemented during the age of the Black Plague, to prevent diseased fleas from getting into the beer.