The compressive strength or crush-extrusion resistance of a gasket material is a major factor with regard to the selection of a given material for use in a particular sealing application. The significance of the test method is based, in part, on the assumption that a material, once it has been crushed or extruded, will no longer function as effectively as a seal. This assumption can only be used as a guide, however, since exact yield or failure points are difficult to define for gasket materials (which are usually viscoelastic in nature). Two or more materials can be compared to determine differences in their resistance to compressive stress. A sample of material can be compared to an established standard or previously determined characteristics on original lots of the same material, for quality assurance purposes. See 6.2 for discussion of specimen area and geometry effects.