Sharpening stoneMade from Wstikivi phyllite, this sharpening stone can be used to sharpen all Roselli knives, but is slightly less effective in sharpening our harder UHC steel. Suitable for rough and end sharpening. Our recommendation is to keep your stone wet when sharpening, this dissipates frictional heat and facilitates smooth sharpening action. Since its a natural stone, each product is unique and the grit value may vary. Natural whetstone lasts many decades.