Felix, I found a set of 4 "Tupperware like" containers at the Dollar store. One of them will just fit inside the Priority Mail Flat Rate Envelope. They are called Good Cook RE-USABLE Containers. The size is listed as Large Square. I estimate they would hold between 2 and 3 pounds of lanolin. The price is 4 for $1.00. Outside dimentions are 2" high x 6" x 6". It might be safest to put one of these containers inside a zip lock bag as backup. PhotonII (aka Turbo)