The Forney 71819 4-1/2-inch type 27 Mounted steel grinding wheel is an aluminum oxide metal grinding wheel. Designed for metal grinding, metal abrasion, body work, metal fabrication and general repair work. Used on ferrous materials. For use on right angle grinders. 4-1/2-inch (114.3 mm) by 1/4-Inch (6.35 mm) with 5/8-inch -11 threaded arbor. A24r-bf with max 13, 300 RPM.