Check the listing for details. 4pack Knife Sharpening Stone Triangle 400/600 Grit. Condition: New. Listed at 19.01 USD. 1. Material: Green silicon carbide is a material with extremely high hardness, making it an excellent abrasive and grinding tool material capable of effectively cutting and grinding other materials, due to its high hardness, it also possesses outstanding wear resistance, it can withstand wear and abrasion, making it widely used in the manufacturing of abrasives and grinding tools.2. Instructions: The recommended angle is typically around 30 degrees, but this may vary depending on the specific blade and sharpening requirements, using moderate pressure, move the knife or tool back and forth across the sharpening stone, maintaining a consistent angle, continue sharpening with smooth, alternating sides regularly to maintain even sharpening.3. Features: The sharpening stone has different grit levels.