All companies supplying the US government use UID (Item Unique Identification) as part of their product or packaging of their product. The UID is intended to provide a machine readable unique identifier that will reduce ambiguity and distinguish one item from another. It is a machine readable mark that consists of either a 2D barcode (usually Data Matrix) or a linear barcode. In addition, there are several human readable fields, including the interpretation of the barcode contents.