The NATO Item Identification Number or National Item Identification Number (NIIN) is a 9-digit alphanumeric code created by the NATO Codification Bureaux to designate unique items of supply.
The NATO Stock Number or National Stock Number (NSN) is a 13-digit alphanumeric code consisting of a Group of Supply, a Class of Supply and the unique NIIN to designate unique items of supply grouped by their relative catalog category.
The first four digits are the NATO Supply Classification (NSC) or Federal Supply Class (FSC) code.
The first two digits are the NATO Supply Group (NSG) or Federal Supply Group (FSG).
Examples: