Model Number: A-21 Key Specifications/Special Features: Grinding wheel abrasive for stone: Material: Aluminum oxide, silicon carbideAluminium oxide: Normal steel, low hardness cast iron, sharpening steel, saws steels rough work, steel finishingSilicon carbide: Marble and natural stones, low hardness cast ron, soft building materials, soft refractory materialsArbor hole size and thickness as per customer's specify when order.A24N: Fast grinding wheel recommended for medium alloy steel. Fast stock removal, good life.A24R: General purpose application on mild and medium alloy steel, cast-iron, weld beads, carpentry steel. Good stock removal long life.A24S: Wheel recommend where a heavy duty stock removal is required, for example application in foundries on mild and medium hardness steel, castings. Fast stock removal and long life.A30P: Recommended on stainless steel, high alloy steel, very hard cast-iron. The wheel is with low iron and Sulphur content for application in nuclear power stations and rust-free applications. Good stock removal andcool grinding.A30N: Aluminum and bronze, other non-ferrous metals. Wheel exempt from loading. Good stock removal and long life.ZA24R: Wheel with zircon oxide content for application on semi-hard and hard castings in foundries .Very fast stock removal and very long life.C24R: General purpose application on masonry, concrete and other building materials, semi-hard and grey cast-iron.