This is a set of six strop compounds by Marbles designed for a variety of uses. The black is designed for removing rust scale, carbon and heavy tarnish. The white is designed for use on chromium, stainless steel, brass and aluminum. The brown is for use on copper, brass, bronze, zinc, and aluminum. The red is for adding a high luster to gold, silver, sterling, nickel and platinum. The blue is for adding a high luster on stainless steel, aluminum, brass and plastics. The green is designed for polishing, lapping, stropping and honing wood working tools.