DEWALT EXTREME? Flap Discs are perfectly suited for grinding and removal tasks on surfaces with an angle up to 15?. It is designed to remove rust, and will grind and clean ferrous metals, made with tough and durable zirconia grain. DESCRIPTION: Resistant, durable zirconium oxide grain. Very robust and resistant, with very high removal rate. Zirconium oxide grain allows a 3x faster material removal than conventional resin-bonded fibre discs. Type 27 design for grinding angles of 0-15 degrees.