Most mouthpieces are made out of brass which can contain up to 3% lead.  The lead in the brass is one of the components that give this particular brass its hardness or rather its softness which makes it have a pleasing sound to musicians. Proposition 65 from the state of California requires manufactures to label any products that have compounds in them that have been found to cause Cancer or Reproductive Harm. Lead is one of these compounds. Bari Woodwinds, Inc. mouthpieces are electroplated with a layer of copper, then a layer of Nickel, Silver, Rhodium or Gold. This electroplating ensures that the raw brass is never in contact with the player.