You have to be careful with either plastic or aluminum. I used a similar aluminum locking box successfully for years; it even worked after it dented. A rigid plastic container cracked with only modest use, while a more flexible plastic sandwich box is still useful a couple of decades later, after a lot of use.. The great thing about aluminum is the ability to heat water over a flame, something not possible with plastic, unless you use a stone boiling technique. I wonder, has anyone tried to heat water in a plastic container using hot rocks?