The Forney 72756 4-Inch Knotted Wire Cup Brush is ideal for fast, heavy-duty cleaning of large metal surfaces and edge blending. This brush is also perfect for the removal of burrs, spatter, weld scale and rust. This tool is designed for right angle grinders and .020 wire. This knotted cup brush has a 5/8”-11 threaded arbor and a max RPM of 8,000