20 PC 3 Inch Discs R Type Sanding Abrasives The National Standard Inc. abrasive Disc is a Sanding/ Grinding disc for removing paint, rust and welds in collision repair. Its small diameter makes it especially useful in hard-to-reach areas. Convenient Roloc compatible attachment securely locks the disc in place with a simple twist, and allows for disc removal just as easily. And the grades are marked on the back of the Disc for fast, accurate identification.