The Mercer 621030 is a 4” x 1/4” x 5/8” Depressed Center Masonry Grinding Wheel. The metal grinding wheel is used for grinding all ferrous metals, steel, structural steel, rebar, bar stock, pipe and welds. The grinding wheel has an aluminum oxide grain which increases the life of the wheel. The wheel is also internally reinforced with layers of high tensile strength fiberglass and has a dual grit blend.