Stoppers is a truncated conical piece of rubber or cork used to close off a glass tube, piece of laboratory glassware, a wine bottle or barrel and containers with orifices. A rubber stopper is also called a rubber bung, and a cork stopper is called cork. Ground glass stoppers are commonly used with laboratory glassware, mainly because of their nonreactivity. They come in many forms such as cork, rubber and plastic film that stretches over the opening.