The AccuSharp TriStone Knife Sharpening System provides easy sharpening and honing for any straightedge blade. AccuSharps threestone surfaces includes coarse medium and fine aluminaoxide stones. This TriStone System provides extra durability and safety on any surface with a rubbergrip base which prevents sliding while sharpening and honing your knives. The TriStone Sharpener base can be mounted to most countertops for extra stability. Includes an angle guide to assist in maintaining a consistent angle while sharpening. Grits Coarse 120 medium 180 fine 240.