3 Pack, 4.5", 36 Grit, Resin Fibre, Aluminum Oxide Steel Sanding Disc With 7/8" Arbor, Ideal For Weld Grinding, Blending, Finishing, Deburring & Other General Purpose Applications, Can Be Used On Most Types Of Steel As Well As Fiberglass & Plastics, Constructed With A Heavy Vulcanized Fibre Back, Coated With Abrasive Grains, & Bonded Together With A Tough Heat Resistant Resin For Fast Cutting Action & Long Life, For Use On Right Angle Grinders.