A gasket is a mechanical seal which fills the space between two or more mating surfaces, generally to prevent leakage from or into the joined objects while under compression. … This is typical of some “ring joints” (RTJ) or some other metal gasket systems.

A ring gasket is a gasket with an inner diameter (ID) and outer diameter (OD); a full face flange gasket is similar to a ring gasket, with bolt holes (aligned in a bolt circle) in the surface area between the ID and OD.

A gasket is a mechanical seal which fills the space between two or more mating surfaces, generally to prevent leakage from or into the joined objects while under compression. Gaskets allow for “less-than-perfect” mating surfaces on machine parts where they can fill irregularities.