A special round combination stone, specially-shaped to fit conveniently in the palm of a hand for the circular motion needed to sharpen & hone axes, hatchets, splitting mauls & machetes. Use the dark gray side, the coarse side, to start a new edge or remove nicks & chips. Use the medium gray side, the fine side, for refining & maintaining a keen edge. The combination stone is made ofpremium dual grit silicon carbide abrasive.Norton Crystolon.

To obtain best results, lubricate your stone with genuine Norton Sharpening Stone Oil. Oil acts as an effective lubricant during sharpening to float away metal & abrasive particles that would otherwise clog up the stone. When metal particles clog the stone pores, it's called glazing & can ruin the stone.

From the Manufacturer:

Norton Sharpening Stones are made of the highest quality materials & are unequaled for long sharpening life, maintenance of shape & smooth cut.