Gaskets allow irregular mating surfaces to be filled on machine parts. The liner is usually produced by cutting from sheet material.
Gaskets for specific applications, such as high pressure steam systems, may contain asbestos. However, due to the health hazards associated with asbestos exposure, non-asbestos gasket materials are actually used.
It is generally desirable that the pads be made of a material produced to a degree such that it deforms and fills the space for which it is designed closely, including any slight bumps. Some gaskets require the sealant to be applied directly to the gasket surface to function properly.
Some (pipe) liners are made entirely of metal and rely on the seat surface to complete the seal; using the metal's own spring properties (up to but not exceeding σy, the material's yield strength). This is typical of some "ring joint" (RTJ) or some other metal gasket system. These joints are called R-con and E-con compression type joints