Our Advantage Zirconia Flap Discs are 4 1/2 inch diameter for small angle grinders.  The are 1/2 inch thick with resin coated paper backing. The 5/8-11 Metal arbor hub locks for added safety. These zirconia flap discs for sale are ISO 9001 certified and have a maximum RPM of 13,300.  The 80 grit rating is fine for light sanding and polishing of steel.