How to read an NSN cross-reference (with a real one)

The number itself

A National Stock Number is 13 digits, written as 4-2-3-4: for example 6340-01-575-3823. The first four are the Federal Supply Class, a category (6340 is aircraft alarm and signal systems; 1680 is miscellaneous aircraft accessories; 2840 is gas turbine components). The remaining nine are the NIIN, the National Item Identification Number, and the NIIN alone identifies the item everywhere in the system. The first two digits of the NIIN are the country that catalogued it: 00 and 01 are the United States. Search either form here; /parts lists the classes with activity.

Why one part number has several stock numbers, and one stock number several part numbers

The cataloguing system assigns a stock number to an item as the government defines it, not to a manufacturer's part. If two manufacturers make interchangeable parts, both part numbers hang off one NSN. If a manufacturer's part number is used in two non-interchangeable configurations, it can appear under two NSNs. The cross-reference table on a stock-number page lists every part number filed against it, each with the CAGE code of the company that assigned that part number.

Reading the reference codes

Next to each part number you will see two codes from the federal logistics record. The reference number category code (RNCC) says what kind of reference the part number is: 3 means a design-control reference, the drawing the item is built to; 5 is a secondary reference; 7 means the number was replaced. The variation code (RNVC) says how interchangeable the item is with the part number: 2 means fully interchangeable, 1 means not fully, 9 means the number is reference only. A part number with RNCC 3 and RNVC 2 is the one you want to quote against. The CAGE status column says whether the company is active in the government's register.

The management data

The acquisition advice code (AAC) is the single most useful letter on the page. D means DLA stocks and manages the item, so it is bought regularly; J and K mean not stocked, bought only on demand; V and Y mean the item is terminal. The FLIS unit price is what the government carries the item at, which is often years old; the buy history below it is what was actually paid. The unit of issue matters when you quote: a price per EA against a request in BX will be thrown out.

Demand and price history

Below the cross-references, a stock-number page shows every open request from DLA and every other agency, then the buy history: who won, how many, at what unit cost, and the median unit cost over three years. That median is your first sanity check on a quote. Sellers with confirmed stock are listed last; if the list is empty, the watch button emails you when that changes.

Try it on a real one: NSN 6530-00-000-0070, or search any number from the home page.