DMT WS7K Mini Diamond Ski & Snowboard Stone - Kit of 3 stones Superior diamond sharpening stones Legendary quality Made in the USA Quick edge repair anywhere Three different diamond stones in fine for a razor sharp edge, coarse to transform a dull edge and extra-coarse diamond to repair a damaged edge Sharpens knives faster than conventional stones with DMT's monocrystalline diamond surface No oil is needed-sharpen dry or with water Durable construction will provide years of consistent performance and reliable service