General description W8 double sided (combination) diamond whetstones are designed for durability and precision. They will not break, chip, crack, hollow, or groove, making them an ideal choice for honing all hard materials, including carbide and steel. These ultra-precision whetstones are lightweight and feature a totally rigid construction, ensuring effective sharpening without the mess of oil. Technical specifications Length: 200 mm Black: Extra Coarse Grade 220, 60 micron Blue: Coarse Grade 325, 45 micron Red: Fine Grade 600, 25 micron Green: Extra Fine Grade 1200, 9 micron Usage Use water for lubrication; no oil is required. The Green side is suitable for quality knives, woodworking tools, and T/C tooling. The Red side is suitable for all woodworking tools, carbide tooling, router bits, and 3D bits.