The search results provided do not contain information about a specific product called "Rainbow Bridge." Instead, they refer to various memorial and sympathy products related to pet loss, such as personalized memorial signs, gift boxes, and bracelets. The materials used in these products include natural wood for signs, saponified coconut, palm, castor, and safflower oils for soaps, and unspecified materials for gift boxes. The ingredients are not relevant to the search query. If you have a specific "Rainbow Bridge" product in mind, please provide more details so that I can assist you further.