A rubber stopper is a small, tapered plug made from rubber that is commonly used in laboratory settings to seal containers or apparatus. Rubber stoppers are available in a variety of sizes and shapes to fit different containers and are often used to seal test tubes, flasks, and other types of laboratory glassware.

They can also be used to seal off a single tube or to connect two tubes together. Rubber stoppers may have one or two holes drilled through them, depending on the intended application. Stopper with a single hole is commonly used for inserting thermometers, probes, or other instruments, while stopper with two holes are used for connecting tubes, adding gas, or for filtration purposes.

The rubber material provides a secure and airtight seal, preventing leakage of the container’s contents and avoiding contamination from the outside environment. Rubber stoppers with one or two holes are versatile and essential tools in many laboratory procedures, allowing for a range of different manipulations and applications.