Covington's magnetic backed dot laps have nickel plated diamond rings evenly spaced across the surface with small interruptions that allow for less loading of disc.  Magnetic backed diamond discs are super-fast to change and now available in five grit sizes, Extra Coarse-60g, Coarse-100g, Medium-260g, Fine-360g, and Extra Fine-600g. These discs have a 1" hole to center on plate. Use in combination with Covington's 12" Horizontal Beveler/Grinder for optimum performance.