Every item cataloged in the U.S. federal supply system carries a four-digit Federal Supply Class (FSC), and that code is usually the first filter a buyer applies. This directory organizes NSN parts by class, so procurement teams can move from a commodity category to individual stock numbers and part numbers.
What Is a Federal Supply Class (FSC)?
A Federal Supply Class is a four-digit code that groups items with similar physical or performance characteristics for supply management. It forms the first four digits of every National Stock Number (NSN). Classification follows what an item is and does, not who makes it. Connectors from different manufacturers can share one FSC, which is why a class works as a search filter across suppliers.
FSG vs FSC vs NSN: What Is the Difference?
The three terms describe different levels of the same code. Take NSN 1560-01-163-1576, an airframe modification kit:
Federal Supply Group (FSG): 15, the first two digits, covering aircraft and airframe structural components.
Federal Supply Class (FSC): 1560, the first four digits, narrowing the group to airframe structural components.
National Stock Number (NSN): all 13 digits, identifying one specific item.
The last nine digits form the National Item Identification Number (NIIN), here 01-163-1576. Its first two digits are the National Codification Bureau (NCB) code, which shows the cataloging country; 00 and 01 indicate the United States.
Buyers should therefore match on the NIIN as well as the full NSN, since the class prefix can change if an item is reclassified. In practice, the FSC tells a buyer which commodity family to search, while the NIIN and part number confirm the exact item before a quote is requested.