A National Stock Number is simply the official label applied to an item of supply that is repeatedly procured, stocked, stored, issued, and used throughout the federal supply system. It is a unique item identifying series of numbers.
The NSN is officially recognized by the United States government, the North Atlantic Treaty Organization (NATO), and many governments around the world. Federal Agencies, including the Department of Defense (DOD), use the NSN to buy and manage billions of dollars worth of supplies yearly. Currently, there are over 6 million NSNs in the federal supply system.