Our Advantage Zirconia Flap Discs are 4 1/2 inch diameter for small angle grinders.  They 1/2 inch thick with resin coated paper backing. The 7/8 inch arbor hole has a durable metal outer layer.  The 7/8 inch arbor is standard on 4 1/2 inch angle grinders but does require a retaining nut that comes with the grinder.  These zirconia flap discs for sale are ISO 9001 certified.  They have a maximum RPM of 13,300 .  The 80 grit zirconia is considered a fine grit for light sanding and polishing.