The IDN is an alphanumeric code assigned to identify end item requirements, major components, generic groups of items required to support fleet marine force organizations (e.g., clothing, tanks, radio sets), depot reparable and modification kits.

The first position in the IDN is numeric. The second position may be alpha or numeric. Positions three through five are numeric followed by an alphabetic character.

When different models of equipment to which IDNs have been assigned are functionally interchangeable, the same five digits are assigned these equipments, but are suffixed by different alphabetic characters.