2 pack disc for bare surfaces. Can be used on many surfaces including metal, wood and fiberglass. Designed for use with 7 inch angle grinders. Fiber reinforced backing is coated with a durable cubitron mineral. Stays sharp resulting in less surface burning, more consistent sanded surface and a longer disc life. Cuts 3 times faster and lasts 3 times longer, resists tearing, and is clog resistant for less work