178-602 Mitutoyo Surface Roughness SpecimenMitutoyo Surface Roughness Specimen Designed for use with the following Mitutoyo Surface Roughness Testers SJ 210 SJ 310 SJ 411 The surface roughness specimen displays a known roughness value. You would use this specimen to help set your Surface Roughness Tester to the known roughness value. The Surface Roughness Tester would then be used to determine the roughness of your parts by comparing that roughness to the roughness of this specimen.