Gator Fiber Disc are designed to be used on angle grinders with a backer pad for aggressive sanding of metal, fiberglass and painted surfaces. Resin-bonded to resist heat and humidity for longer life. For used with 7" backer pad model #3018. 3 Pack Size: 7" x 7/8" Backing Type: Cloth Grade: Extra Coarse Grain: Aluminum Oxide Grit: 36 Grit - Extreme Removal RPM: 8600 For used with 7" Backer Pad #3018 Resin-bonded to resist heat and humidity for longer life Designed to be used on angle grinders with a backer pad.