Estone Ruby Sharpening Grindstone Whetstone Oilstone Grit 3000 Sharpener System Tool The Ruby Sharpening stone is Light, portable, and Anti-friction Its extremely hard, maintain their shape well and are resistant to wear Install easy in the a tool or machine, also easy sharpening and polishing all kinds of exact knives For sharpening and polishing chilled steel, alloy steel and precision parts etc Sharpening stone can use oil or water