Silicon Carbide Black Resin Fiber Disks 7x7/8 - 24 Grit . Black resin sanding discs have electrostatically deposited silicon carbide grains for superior cooler cutting action. These resin fiber discs last 2-3 times longer than conventional grains and work great on stone, masonry, and composite plastics. Requires backing pad, For use with Right Angle Grinders. Condition is New and 25 Disks per Package!!!