Abrasive Type 18R grinding plugs are made of an aluminum oxide grain with a large grit size for heavy-duty grinding and snagging in hard to reach places and for fast stock removal on ferrous metals such as iron, steel, welds, etc. 1 1/2\\\\\\\" Diameter, 3\\\\\\\" Long, 5/8-11 insert For angle grinders with a 5/8-11 shaft.