Two sets are available each comprising three diamond stones. Available sizes are 25 x 75mm, or 50 x 150mm. Supplied in one of each grit 180, 260 and 360, colour coded for ease of identification. Use them for sharpening or touching up all manner of small tools, chisels, pocket knives or router cutters. Use a little water as lubricant and dry after use. Blue = 180g, Yellow = 260g, Red = 360g.