Gator, 3 Pack, 4.5" x 7/8", 50 Grit, Aluminum Oxide Fiber Discs, Designed To Be Used On Angle Grinders With A Backer Pad For Aggressive Sanding Of Metal, Fiberglass & Painted Surfaces, For Used With 4.5" Backer Pad #3017, Resin Bonded To Resist Heat & Humidity For Longer Life.