Gasket

A GASKET is meant to form a mechanical seal that fills the space between two or more mating surfaces. Its goal is to prevent leakage from, or into, the joined objects while under compression.
There are many different types of gaskets used in the oil and gas (petrochemical) industry and other heavy industry. They include both standard ANSI/ASME pipe flanges (an example is ASME B16.5 flanges) and gaskets used in heat exchangers.