RS PRO Surface Gauge Set Use these RS PRO surface finish testers to quickly and reliably evaluate your machining work. Simply compare the surface finish on your machined components or parts to the surface of these precision-engineered reference plates. Tactile comparison can be done by scraping a fingernail across the surfaces, while you can use a magnifying lens for visual inspection. Designed to evaluate six machining methods - flat lapping, external grinding, grinding, horizontal milling, vertical milling and turning - the comparators cover a range of surface geometries. The plates come stored in an easy-to-carry PVC wallet. This holder has labelled slots for each tester to keep them organised and features a handy usage guide. The comprehensive set of 30 pieces suits the vast majority of machining applications. These plates are regularly used in engineering workshops, drafting rooms and for quality-control applications. Features and Benefits - Set of 30 surface finish testers - Plate dimensions of 3/8 in x 7/8 in - Supplied in a PVC wallet - Made from carbon steel - Accuracy within permitted tolerance of ±12%