SAIT 41000 buffing compound kit contains brown, white, red and black bar. Brown bar used for buffing aluminum, brass, copper, wood, plastics, hard rubber and painted surfaces. White bar used for buffing stainless steel, carbon steel, nickel, aluminum and chromium to a high luster and shine. Red bar for buffing precious metals like gold, silver, platinum, sterling and other high end metals. Black bar used to buff contaminants out prior to finishing, will remove rust, stains, scale and other contaminants.