Fine Rough grinding and polishing with the same abrasive tool: With the Dronco Grind and Polish System GPS Dual now makes this possible. The system consists of a 125mm Flap Disc and inserted into this is a 90mm flap disc with a different grain. Both discs are mounted together on the angle grinder. The change between rough and fine grinding is controlled by the pitch angle of the grinder: 30% angle: rough grinding, 15% angle: fine grinding. Zirconuim discs in different grits and polishing fleeces in different grades allow a variety of combinations.