This is a 2-pack of the FINE grade (30 micron/400 grit) of the 3M microfinishing diamond family. Perfect for hard materials such as semi & precious stones, carbides, cobalt, tungsten, chilled iron, etc. Use wet or dry. Follow up with VERY FINE grade for finer finish. Uses for Microfinishing Diamond Abrasives include: For Lapidary & Watch Crystal: Ideal for cutting & shaping stones as well as smoothing out chips. Also removes heavy to fine scratches on watch crystals. For a higher polish on your stones or glass, use the 3M™ PREMIUM Polishing Diamond Kit after these Microfinishing Diamond abrasives. For Carbide Tools: Sharpen router bits, forstner bits, shaper cutters and various other tools & remove chips. The sharper-than-factory finish reduces heat build-up during tool operation.