A National Stock Number (NSN) is a 13-igit numeric code, identifying all the 'standardized material items of supply' as they have been recognized by the United States Department of Defense. Pursuant to the NATO Standardization Agreements (STANAGs), the NSN has come to be used in all treaty countries, where it is known as a NATO Stock Number. A two-digit Material Management Code (MMC) suffix may also be appended (see ), but it is not considered part of the NSN. An item having an NSN is said to be "stock-listed".