Arbor Mount Sanding Disc, Vacuum Hole Design No Hole, Disc Dia. 4-1/2 In., Grade Fine, 120 Grit, Abrasive Type Closed Coat, Resin Bonded, Abrasive Material Proprietary Blend, Backing Material FiberMounting Hole Size 7/8 In., Color GrayPackage Quantity 25 Abrasive Fiber DiscsFull resin bond and fiber backing for strength, durability, and tear resistance. Use on right-angle grinders with back-up pads, sold separately on page 3718.4" discs have 5/8" arbor hole 4-1/2" and larger discs have 7/8" arbor hole Sold in pkg. of 25ARC PREDATOR Premium blend of proprietary grains and grinding aid with heavy fiber backing. Ideal for grinding mild steel and carbon steel. Performance-coated discs are designed for aluminum, soft metals, and alloys. Proprietary coating resists loading for high cut rate and performance.