A bell jar is a glass vessel that is used in laboratory settings to create a vacuum or to protect samples from the external environment. It typically has a cylindrical shape with a flat base and a dome-shaped top. A stoppered bell jar is one that has a rubber or cork stopper that can be inserted into the opening at the top of the dome-shaped cover.

This creates an airtight seal that can be used to create a vacuum inside the bell jar or to prevent air or contaminants from entering. Bell jars with stoppers are commonly used in chemistry and biology laboratories for experiments that require a controlled environment, such as chemical reactions, vacuum filtration, or plant growth experiments.

They are also used in physics experiments, such as demonstrations of the effects of air pressure on objects or for creating a vacuum for high-voltage experiments. The stoppered bell jar is a versatile and essential tool for laboratory work and is available in various sizes to fit different applications.