SaitZ-tech High Performance Z24R are United Abrasives grinding wheels constructed for the toughest applications. They are made of tough zirconium, have a course grain size and a medium hard bond. Applications: Ferrous metals such as iron, steel and welds as well as stainless steel and high tensile alloys. 4 1/2" diameter, 1/4" thick, Type 27 (depressed center), 7/8" bore, no hub. For right angle grinders.