Spyderco's 3" X 8" X 1/4" ultra-fine ceramic benchstone is flat, thin and ultra smooth for professionally finishing and sharpening wide tools like chisels, large blades, wood-working equipment, plane irons, even ski and snowboard edges. Made from Alumina Ceramic, it is manufactured in the United States using a process where a binding agent is combined with Alumina particles that are actually synthetic sapphires. The stone is shaped then kiln fired to temperature of 3000 degrees F (1649ËšC). Alumina ceramic stones measure 9 on the Mohs hardness scale (out of 10) and don't require lubricants like oil or water for use. The ultra-fine grit stone tightens and smoothes the cutting edge's scratch pattern for an even keener, hair popping edge. The stone is thin and light enough for hand held use, taking the sharpening surface directly to larger items. We recommend when tabletop sharpening, using the stone on top of its suede carrying case for slip free use. To clean the stone, wash it in fresh water and scrub with a powdered abrasive cleaner and a scouring pad. Rinse and air dry. 3" x 8" x 5/16" (76.2mm X 203.3mm X 8mm).