The Ace Tool Type R Mini Resin Grinding Discs are manufactured using a multilayer, heavy duty vulcanized fiber backing, and they are covered with a formulated bond coat to resist loading, glazing and grain stripping. An advanced bond extends disc life by minimizing grain shredding, while promoting a cool grinding action to reduce glazing and loading. Designed to be powerful, versatile, flexible, safe and economical, Ace Tool Type R Mini Resin Grinding Discs are available with an aluminum oxide or zirconia abrasive grain.