The CARBORUNDUM Quick Change Disc, model 369TE4, is a 4-1/2 inch diameter x 7/8 inch thick Type 27 depressed center grinding wheel made of aluminum oxide abrasive grains bonded with vitrified bond. It has a maximum safe speed of 6600 RPM and is designed for use on portable grinders, stationary tools, and flexible shaft machines for general purpose grinding of ferrous metals. This thin wheel allows grinding in tight areas. It features a Quick Change hub system for fast and easy disc changes.