Stopper (plug)

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A stopper, bung, or cork is a seal that closes a container like a bottle, tube, or barrel. Unlike a lid, a stopper fits inside the opening to seal it. A bung is the term for a stopper used in barrels; a plug is used for steel drums. A glass stopper is usually a ground glass joint, and a cork stopper is simply a cork. Wine bottles are normally closed with corks, even if the stopper is not cork. Metal bungs with threads are sometimes used in barrels and drums.

In laboratories, ground glass stoppers are common because they don’t react with chemicals. Some have holes to let glass tubing or a funnel pass through, which lets gases or vapors be collected or transferred during a reaction. Rubber bungs are used in small-scale experiments to seal flasks and can also have holes for tubing. For tougher needs, standardized glass stoppers and connectors are preferred. Gutta-percha stoppers were an early, chemically resistant option and were among the first products of the Gutta-Percha Company.