Accusharp Tri-Stone Sharpening System Coarse Medium Fine Alumina-Oxide. AccuSharps three-stone surfaces includes coarse medium and fine alumina-oxide stones. This Tri-Stone System provides extra durability and safety on any surface with a rubber-grip base which prevents sliding while sharpening and honing your knives. The Tri-Stone Sharpener base can be mounted to most counter-tops for extra stability. Includes an angle guide to assist in maintaining a consistent angle while sharpening. Specifications for Accusharp 064C Tri-Stone Sharpening System Coarse Medium Fine Alumina-Oxide S: Manufacturer: AccuSharp Grit: Medium Coarse Fine Fabric/Material: Alumina-Oxide Color: Blue/Black Quantity: 1 Handle Material: Rubber Accusharp 064C Tri-Stone Sharpening System Coarse Medium Fine Alumina-Oxide