20 pack 4 Inch flap discs assortment, 40/60/80/120 Grit, each model 5pcs, 5/8 Inch Arbor size, Flap type # 27 flap disk, Max speed 13300RPM,grinding disc 5 8 arbor Made of industrial grade aluminum oxide abrasives, high strength durability anti-static and anti clogging, long lasting use. Constructed of resin fiber backing will greatly absorb vibration and ensure reinforcement. Sanding disk Recommend for grinding blending stone smoothing surfacing polishing of rust paint metal wood ferrous stainless steel and plastics. Assortment grits will meets most of your polishing and welding work, the flap disks compatible with universal grinders such as Bosch Dewalt, both air and electric sanding grinders.