This combination sharpening whetstone by GLOBAL has been specially developed for use with professional quality kitchen knives. If you follow the detailed instructions enclosed in the packaging, you can achieve spectacular results, even exceeding the knives, ex-factory sharpness levels! It is the recommended way to keep your knives in the best condition for use. This stone features 2 different grits - 240 and 1000. The 240 grit is classed as a "course" finish, and should be used when knife blades are chipped, damaged or completely blunt. The 1000 grit is classed as a "medium" finish and is the main stone for sharpening knives which have become blunt.