The mailer must package cremated remains (human or animal ashes) in a sealed and siftproof funeral urn. The mailer must place the urn into a strong and durable outer container, and must pack the outer container with sufficient cushioning material to prevent shifting during transit. The outer container must be siftproof to prevent powders from escaping and thereby soiling, damaging, or destroying another mailpiece or any postal equipment, or from causing discomfort to a person. Also see Publication 52, Packaging Instruction 9F.