These 7/8" silicone wheels contain pumice abrasive that will not mar or scratch most stones when polishing. Use for prong and bezel finishing in already set precious or synthetic stones. Available in medium and fine grits with 1/16" hole, the recommended RPM is 7,000-10,000. Pumice wheels are compatible with our miniature screw mandrels (BRS-274.00 and BRS-275.00).