DEWALT DW8304 4-Inch by 5/8-Inch 120 Grit Zirconia Angle Grinder Flap Disc Zirconia grit enables 3X faster material removal than fiber resin metal sanding discs Premium abrasive cloth provides up to 15 X longer life than fiber resin metal sanding discs Type 27 fiberglass backing provides grinding angle of 5-15 degrees