Dietary Supplement Four Kings consists of four mushrooms that are known for their powerful tonic and protective benefits. This formula is extremely safe and effective. Ca Prop 65 Warning: The use of this product will expose you to lead, a substance known to the state of California to cause birth defects or other reproductive harm. Daily breathing in CA alone will result in lead exposure exceeding CA Prop 65 warning level for birth defects or reproductive harm. The lead content of this product is lower than the FDA standard for lead in bottled water.