Corundum = 89 A, pink - hardness M = medium Type 1, straight, for various bench grinders, tool grinding machines and other stationary grinders. For hardened steel and tools produced from tool and high-speed steels, hardened tool steels. Advice: Plastic adapter sleeves for reducing 32 to 25, 32 to 20, 32 to 18, 32 to 16 are included in all sanding disc packs.