NSNs vs. OEM Part Numbers: What Is the Difference and Why Does It Matter?

In the highly regulated and quality-sensitive sectors of aerospace and defense, having accuracy in part identification is of paramount importance. For procurement professionals, engineers, and logistics coordinators alike, successfully navigating a marketplace often depends on how efficiently one can identify, verify, and source the components they need, with many means available to conduct a search. However, there are two recognized systems that prove to be highly useful for these industries, these being original equipment manufacturer (OEM) part numbers and National Stock Numbers (NSNs).

While both serve as tools for identifying items of supply, they are fundamentally different in their origin, structure, and application. Therefore, understanding these differences is key to avoiding costly procurement errors, ensuring compliance, and optimizing operational readiness. As such, be sure to read on as we provide a comprehensive overview of OEM part numbers and NSNs, comparing their respective roles, benefits, and functionality in the procurement process.

The Importance of Accurate Part Identification

Before diving into the distinctions between NSNs and OEM part numbers, it is helpful to first understand why proper part identification matters. Generally speaking, aerospace and defense operations require the use of parts that meet specific technical and regulatory standards. If one were to employ the wrong part, issues ranging from non-compliance and mission delays to system failures may occur. As such, one always needs to have the ability to verify compatibility, specifications, and traceability, this all being supported by the use of OEM part numbers and NSNs.

What Are OEM Part Numbers?

As the name suggests, OEM part numbers are alphanumeric codes assigned by the original manufacturers of items, such codes serving to uniquely identify products for internal tracking and management. These identifiers are created during design and production stages and are proprietary to the manufacturer that produces the part.

The Key Characteristics of OEM Part Numbers

• Assigned by Manufacturers: Each part number is designated by the OEM of a part, such as Boeing, Honeywell, Raytheon, or General Electric.
• Varied Structures: The structure and format of part numbers will differ by manufacturer and product type, with no single standard across the industry.
• Used in Design and Maintenance: OEM part numbers often appear in aircraft manuals, maintenance documents, and technical schematics.

The Benefits of OEM Part Numbers

• Direct Reference to Manufacturer Specifications: OEM numbers link directly to a part’s intended application, dimensions, tolerances, and certifications, offering useful information during a search.
• Widely Recognized Across Commercial and Military Markets: Buyers familiar with the platform or system they are working on often rely on OEM numbers for quick sourcing.
• Helpful in Repair and Maintenance Planning: Maintenance teams commonly use OEM numbers to identify exact-replacement parts for the objective of system continuity and warranty compliance.

Important Considerations When Using OEM Part Numbers

• Possible Alternate Part Numbers: Some items may have superseded or alternate part numbers, requiring cross-referencing to confirm items.
• Part Number Overlap: As OEM part numbers are proprietary and there is no industry-wide standard, two distinct items from separate manufacturers may have the same part number.
• Not Always Government Approved: OEM parts are not inherently approved for defense use unless additionally validated through NSN data or other regulatory designations.

What Are NSNs?

National Stock Numbers NSNs are standardized 13-digit numeric codes that are assigned by the United States Defense Logistics Agency (DLA) and allied military organizations to various material items of supply. NSNs provide a uniform way to catalog and track items of supply across military and government systems, and they are widely used by NATO nations and other allied countries.

The Key Characteristics of NSNs

• Assigned by Government Agencies: NSNs are typically created by federal or NATO logistics agencies following strict cataloging protocols.
• Structured Format: NSNs are divided into two main parts:
  • Federal Supply Class (FSC): The first four digits of the NSN are the FSC, which classify the item based on use and organize it with similar items.
  • National Item Identification Number (NIIN): The remaining nine digits uniquely identify the item.
• Tied to Multiple Part Numbers: A single NSN may be associated with multiple OEM part numbers that share similar characteristics, even if from different manufacturers.

The Benefits of NSNs

• Standardized Across Governments and Allies: NSNs are recognized internationally, allowing interoperability among NATO partners.
• Simplifies Logistics and Inventory Management: NSNs streamline procurement, warehousing operations, and maintenance through a unified cataloging system.
• Ensures Part Interchangeability: NSNs provide assurance that functionally equivalent parts can be sourced from different approved vendors.
• Supports Contracting Compliance: NSN-based sourcing aligns with military procurement standards and audit requirements.

Important Considerations When Using NSNs

• Potential for Cataloging Delays: Newly developed or specialized items may not immediately receive NSNs.
• Requires Database Access: Efficient use of NSNs for procurement often depends on having access to tools like the Federal Logistics Information System (FLIS) or NSN cross-reference databases.

NSNs vs. OEM Part Numbers: A Review

Both NSNs and OEM part numbers offer value in part identification and sourcing, but they differ significantly in purpose and application. Here is a summary of how they compare:

Aerospace Purchasing: Supporting Streamlined Sourcing

Whether you are working on a government procurement contract or managing repairs for a commercial aircraft, being able to search and source parts using both NSNs and OEM part numbers is crucial for efficiency and compliance. Here on Aerospace Purchasing, a website owned and operated by ASAP Semiconductor, we support both sourcing approaches with:

• Provided search tools with NSN, part number, manufacturer, and description filters.
• Curated OEM part number catalogs and an extensive NSN database.
• Quality assurance through ISO and FAA-accredited sourcing practices.
• Streamlined quotation processes with team members to handle part number and NSN requests.

It is our standing goal to equip buyers with the flexibility, visibility, and confidence they need to make informed decisions in a demanding marketplace, so be sure to choose us for your next project.