These 3/4" diameter, fine Sand discs are manufactured with the grit glue bonded onto one side of thin, flexible plastic-backed discs. . (Sand is a long-lasting white aluminum oxide which is a natural mineral; slightly less aggressive than Garnet.  Recommended for general use and with acrylics and gold.) These thin, flexible, plastic-backed discs reach into tight areas and conform to surface contours.   Since they are manufactured with the Moore Snap-on brass center, they need to be used with a Snap-on mandrel (sold separately).  Max. operating speed: 30,000rpm.  Sold in box of 200 discs.