NSN, NIIN, FSC, CAGE, PMA, TSO, MCRL, AMSC: the glossary

NSN, National Stock Number. Thirteen digits: FSC plus NIIN. The government's identity for an item, independent of who makes it. See any stock-number page.

NIIN, National Item Identification Number. The last nine digits of the NSN; the part that is unique. Two digits of country code, seven of serial.

FSC, Federal Supply Class. The first four digits; a category such as 1560 (airframe structural components) or 2915 (engine fuel system components). Browse the classes with activity at /parts.

PSC, Product Service Code. Used on SAM.gov notices. For supplies it is the same four digits as the FSC, which is how a SAM.gov notice and a DLA RFQ line up on this site.

CAGE, Commercial and Government Entity code. Five characters identifying a company location in the government's register. Every vendor page here is keyed by it: CAGE 9EEV9.

MCRL, Master Cross Reference List. The federal record that maps manufacturer part numbers and CAGE codes to NSNs. The cross-reference table on a stock-number page is drawn from it.

RNCC / RNVC, reference number category code and variation code. Two digits beside each cross-referenced part number saying what kind of reference it is and how interchangeable. Explained in the cross-reference guide.

AAC, acquisition advice code. One letter saying how the government buys the item: stocked (D), bought on demand (J, K), terminal (V, Y). Shown in the management data on a stock-number page.

AMSC, acquisition method suffix code. On an RFQ, whether anyone can quote (G) or only approved sources (H, R, T). Explained in the DIBBS guide.

PMA, Parts Manufacturer Approval. An FAA approval for a company other than the type-certificate holder to produce a replacement part. A PMA part is an FAA-approved part, not a copy.

TSO, Technical Standard Order. An FAA minimum performance standard for a class of article (a radio, a seat belt, a tire). A TSO authorization lets a manufacturer produce articles that meet it.

8130-3. The FAA authorized release certificate that travels with a new or serviced part, signed by the producer or the repair station. The paperwork buyers ask for by number; see condition codes for what should come with each condition.

AD, Airworthiness Directive. A legally enforceable FAA rule requiring inspection or replacement of specified parts on specified aircraft. Shown on part and stock-number pages under the FAA tab.

SDR, Service Difficulty Report. A report filed with the FAA when a part fails or is found defective in service. Counted per part number on the FAA tab.

UPN / SUP, Unapproved Parts Notification, suspected unapproved parts. The FAA's published notices about parts produced or sold without approval. Searchable at /unapproved-parts.

DIBBS. DLA's Internet Bid Board System, where DLA posts and receives quotes on requests below the simplified acquisition threshold.

SAM.gov. The System for Award Management, where every federal agency posts contract opportunities and where entities register for CAGE codes and UEIs.

FPDS. The Federal Procurement Data System, the record of every federal contract action, with the winning vendor and the dollars. The source of the award record on vendor pages and of Market Pulse.