Full size EZ Hone the solution to overcoming one of the major obstacles to knife sharpening-keeping the blade at the proper angle to the stone. The angled wood end blocks are designed to keep the knife blade at the perfect sharpening angle. This 4 stone model comes with Coarse (Silicon Carbide), Medium (Soft Arkansas), Fine (Hard Arkansas) and Extra Fine (True Hard) stones. The different stone grades are as follows: Silicon Carbide (Coarse): man-made stone that is much coarser than any of the natural Arkansas stones. This is the stone to use on very dull or damaged edges. Soft Arkansas (Medium): coarsest, most versatile and most popular of the Arkansas stones. Soft Arkansas stones are used to quickly put an initial edge on dull or neglected knives or other cutting tools. This is a natural stone and color can vary from white to gray/black to pink/gray, or a combination of these colors in a single stone. Hard Arkansas (Fine): used to establish and maintain a keen edge on cutting tools. This natural stone color can include Grey, White, B lack/Grey, Grey/Pink, Black/ White, White or White/ Pink, or a combination of these colors. True Hard Arkansas (Extra Fine): This is a harder stone than the Soft or Hard Arkansas and is used for final polishing and sharpening. It is often referred to as Multi-Colored Translucents as the stone can be both opaque and translucent and may be black, red, white, white/grey or a combination of these colors. Genuine Arkansas stones are 100% quarried in the Ouachita Mountains of central Arkansas. They are highly sought after worldwide for their superior ability to sharpen knives and woodworking tools, as well as to put surgical quality edges on a wide variety of instruments Arkansas stones produce these fine edges s with less wear that man-made stones. All Arkansas stones work best with light mineral honing oil to suspend the metal particles produced by the sharpening process which prevents clogging of the pores of the stone.