Remove high spots and even out gouges, leaving your surface flat enough for polishing. Made with a ruby abrasive, these stones have exceptional hardness and extra coarse grit to remove material faster than standard polishing stones. They also resist wear for long-lasting use. Use these stones by hand or in power tools with a compatible holder (both sold separately). Though not required, you can apply a water-soluble or oil-based lubricant to keep debris from building up.