Tumbling, also known as Mass Finishing, is a technique for smoothing and polishing a rough surface on relatively small parts. Mass finishing media, such as angle cut cylinders, stars, triangles, cones, angle cut stars, wedges, pyramids, and tetrahedrons, is placed in a centrifugal disc machine and spun at high speeds. The media acts as an agent to surface finish parts in various sizes.  In the field of metalworking, a similar process called barreling, or barrel finishing, works upon the same principles.