The primary function of a package enclosing a sterile medical or surgical device (e.g. syringe, needle, scalpel, etc) or a tray wrap enveloping a set of surgical items is to be an absolute barrier towards micro-organisms. Generally, the barrier function operates from the time that the item is exposed to the sterlization treatment until it is used. It follows that the material(s) constituting the package or wrap must permit the sterilization treatment to perform effectively, yet present a barrier to potential microbiological contaminants during post sterlization storage, handling and transport.