5" or 6" diameter disc for use with a random orbit sander PSA attachment permits quick and easy disc changes Aluminum oxide grit is a common choice for general-purpose grinding of wood, metal, fiberglass, and plastic, and is more durable than silicon carbide grit Zinc stearate coating prevents clogs from forming and extends the life of the abrasive C-weight paper backing is flexible, slightly stronger, and more rigid than A- and B-weight paper, and provides a more consistent finish than fiber or cloth backings