Product Details: What is a National Stock Number (NSN)?

You’ve stared at it many a times. You’ve seen those numbers. You read what they are. But, do you understand them? What is an NSN and what does it refer to?

Sure you can search for it, but try to type in “NSN” in Google or Yahoo or whatever and you are liable to get anything from “Never Say Never” to “No Such Number” to the “National Storytelling Network.” To be clear, we are discussing the National Stock Number, which also goes by the name, NATO Stock Number.


Figure 1 – Where a National Stock Number appears on a SkyGeek product page. (CLICK TO ENLARGE)

At a quick glance an NSN is nothing but a 13-digit code but upon closer inspection it is much more. In order to fully grasp the scope of this code you must study its structure. Firstly, it is not simply a string of 13 numbers, one after another. And it isn’t necessarily a number. It is a code. What’s the difference? A code can be alphanumeric, i.e. not only numbers. However, it usually consists mostly of numbers.

Generally, an NSN will appear with dashes although it doesn’t have to. When it does include dashes it look something like this: 1111-22-333-4444.

An NSN is broken into two sections: a 4-digit FSCG and a 9-digit NIIN. FSCG stands for “Federal Supply Classification Group”; NIIN stands for “National Item Identification Number.”


Figure 2 – An NSN is broken into two parts: the FSCG (the prefix) and the NIIN (the root). These two parts are separated and juxtaposed courtesy of (CLICK TO ENLARGE)

The FSCG is further divided into a 2-digit Federal Supply Group (FSG)—which is the first two digits—and the actual FSC, or Federal Supply Class; this makes up the last two digits in the 4-digit code. For a nice idea of FSCs and what they mean, you can check out ArmyProperty’s listing. And as if to confuse you even more, the FSCG is also known as the National Supply Classification Group (NSCG). Overall, the FSCG serves as a prefix to the NIIN; its function in an NSN is to provide context, so that the general classification of a specific item can be identified.

Similar to the FSCG, the NIIN is divided into two sections. The first two digits designate the National Codification Bureau (NCB) code. This refers to a country’s agency that deals with the NATO Codification System, or NCS. For example, the United States has a NCB code of 00 or 01 while 15 is the NCB code for Italy. The NCB thus gives you an idea of what entity is in charge of dealing with a particular item. The remaining seven digits uniquely identify the item.

For the sake of clarity, let’s use an item from our site and deconstruct its NSN. For this example we will use the MS51958-64 Machine Screw, which has the following National Stock Number: 5305-01-541-2751 (See Figure 3).


Figure 3 – An example of how an NSN is broken down into smaller codes. (CLICK TO ENLARGE)

Based on Figure 3 you can see this item has the FSCG, 5305. The 53-code is the FSG classified as “Hardware and Abrasive” while the 05-code (the FSC) identifies the item as a “Screw.” As for the NIIN, the NCB is 01. As mentioned earlier, that NCB alludes to the United States so it was made there. The actual item number, 5412751, does not have any significance of any kind and thus cannot be broken down any further. Thus, you can see that in an NSN, the most important part is the NIIN—especially the last seven digits. That will narrow down your search if you want to find a precise item.

The aforementioned screw is a fastener made to conform to military specifications. And a great portion of NIINs are specially designed with the military in mind. Still, NIINs are not limited to items used exclusively by the Armed Forces so that when you factor in what are classified as “Items of Production,” you’re looking at a coding system that contains over 16 million NIINs!

So who is responsible for National Stock Numbers and cataloging such a massive classification system? Who else but the U.S. Department of Defense.

With so many items to keep track of, it is only natural that a classification system would exist. And when you (well, a government entity) are handling over 32 million parts that belong to countless systems for countless equipment and vehicles, you want to be able to trace each one easily and efficiently. The NSN, while confusing to the average person, makes sense to those trading and acquiring parts for the items that are an integral component to their work operations.

This entry was posted in On Site by Skylar
. Bookmark the permalink.

About Skylar

Woah! This is Skylar. I am THEE Sky Geek. I like planes, trains, and automobiles, but really just planes. I love aviation and anything related to it. If you shop on our site you will see my mug plastered throughout since I am the official mascot. I enjoy talking to Sandy, Otto, and Mach since they share my passion for flight. Researching for news and events and other information that affects our customers is what I can't wait to nose dive into. The sky's the limitless!