A new garbage bag (still folded from the factory) is as close to sterile as you're going to get in the field. It is larger than the size of a dressing package and in my opinion, most of those bags are usually too small to carry the intestines in, from an evisceration type of wound. The main idea is to get the victim ready for an immediate medevac to a hospital that can clean everything up AND get things back where they belong without any kinking.