U series:
White is used for grinding the porcelain teeth artifacts.
Pink is used for rough selling of ceramic and alloy workpieces.
Blue is used for the polishing of porcelain teeth, precious metals, jewelry, etc.
Black is used for grinding the cobalt-chromium alloy and hard metals.
Green was used for the preliminary polishing resin.
Brown for quick polished metal, resin plastic.
Yellow is used for polishing resin, jewelry, etc.