Pearl Abrasive Silver Line Flap disc comes in Aluminum Oxide or Zirconia abrasive grains. It is a lower cost yet still high quality flap disc. Pearl Abrasive uses the best material for backing and only the finest quality abrasive grains. These flap discs embed the fine quality grains to a durable polyester / cotton backing that increase the life and the quality of these Flap Discs. Call Trans American Products today with any questions on Pearl Abrasive Co. Flap Discs.