These medium grit, 7/8” Knife-Edge (22x4mm) EVE® pumice wheels have a 1/16” center hole (mandrels sold separately). EVE® pumice polishing wheels are the ideal rubber abrasive on the bench for working on settings and other metals and best of all, will not scratch stones! The medium pumice abrasive is safe to use around most stones and polishes/burnishes out most scratches and imperfections on metal surfaces. For optimal results, use at 7,000–10,000rpm with very little exertion of pressure. Sold in a package of 100. Thickness: 3.5mm (with a tolerance of 0.5mm). Made in Germany.