A muselet is the traditional wire cage fitted over a Champagne cork.
Its purpose is practical: the carbon dioxide pressure inside a Champagne bottle can force the cork out unexpectedly. The muselet holds the cork against the bottle lip, while a foil capsule and sometimes a paper or plastic covering complete the familiar top of the bottle.
The wire cage is usually secured by twisting a wire loop several times around the bottle’s neck. Many producers place a branded metal plaque, called a plaque de muselet, beneath the cage. Collectors often save these plaques, which can feature elaborate designs and identify the producer or a special release.
A muselet is not the same as a pupitre, which is a riddling rack, or a bidule, which is a small plastic insert used in some bottle-fermentation processes. Careful opening remains important even when the cage is still attached.