A military washer is not simply a commercial washer with a different name on the label. Military-specification, or mil-spec, washers are manufactured to documented standards that define dimensions, material, finish, and traceability, not just the physical shape of the part.
Three standards systems govern most of the mil-spec washers used across defense and aerospace programs: AN (Aeronautical Standard), NAS (National Aerospace Standard), and MS (Military Standard). Each system serves a distinct role, and understanding the difference matters for anyone specifying or sourcing these parts.
This article is written for engineers, procurement specialists, and sourcing teams working on defense and aerospace programs who want to understand what these standards mean before making a sourcing decision.
Editor's Note: The information provided in this article is intended for general informational purposes only and should not be interpreted as engineering, design, material selection, or application-specific guidance. Material requirements and specifications vary by application and should be evaluated according to individual project requirements.
What Are Military-Specification Washers?
Military-specification washers are washers manufactured and certified to standards established by the U.S. Department of Defense and related aerospace and defense standards bodies. What separates a mil-spec washer from a commercial one is not just its shape. The applicable standard defines material specification, finish, testing methods, and documentation requirements in addition to dimensions.
Mil-spec parts are commonly supplied with certification paperwork, including material certifications, lot traceability records, and dimensional inspection reports. Commercial washers commonly are not.
This distinction matters in defense procurement because engineering drawings and program documentation often call out a specific standard by number. A commercial washer with matching dimensions is typically not considered an acceptable substitute, even when the dimensions match.
Mil-spec washers are commonly found in military aircraft, rotorcraft, ground vehicles, naval vessels, defense OEM assemblies, and aerospace structural components.
Browse the military washers collection to see the specifications Superior Washer stocks.
AN, NAS, and MS: The Three Military Washer Standards Systems
Three separate standards systems cover most of the mil-spec washers used in defense and aerospace applications. Each is governed by a different body and is commonly applied in different contexts.
AN Series: Aeronautical Standard
AN stands for Aeronautical Standard, a series originally developed for U.S. military aircraft. AN standards are governed by the U.S. military services and are widely adopted across aerospace and defense programs.
AN washers are commonly found in aircraft, rotorcraft, and aerospace assemblies where dimensional consistency and material traceability are required.
AN960 is among the most widely specified mil-spec flat washers in aerospace and defense. It is a general-purpose flat washer used across a broad range of fastening applications.
AN961 is a countersunk, or beveled, flat washer designed to seat against the angled bearing surface of countersunk fastener heads in flush-mounting aerospace and military applications.
AN901 is a copper or aluminum seal washer commonly used for hydraulic and fluid line fittings. AN970 is a large outer-diameter flat washer that provides a significantly larger bearing surface than AN960 and is commonly found in assemblies with soft, composite, or thin sheet materials.
NAS Series: National Aerospace Standard
NAS stands for National Aerospace Standard, a series developed by the Aerospace Industries Association (AIA) covering aerospace and defense fastener components.
NAS standards are commonly specified in aerospace structural applications and defense programs that call for tighter dimensional tolerances and certified traceability.
NAS1149 is one of the most frequently specified NAS washers in aerospace structural fastening applications. NAS620, NAS1515, and NAS1587 cover additional flat washer configurations within the NAS system.
MS Series: Military Standard
MS stands for Military Standard, a set of standards established by the U.S. Department of Defense covering a wide range of military components.
MS washers are specified across the full range of defense applications, including ground vehicles, naval vessels, military aircraft, and defense OEM assemblies - this includes MS15795, MS16212, MS20002, and MS21206 to name a few.
The MS series is the broadest of the three systems, covering the widest range of washer configurations and material specifications. Each MS number corresponds to a specific standard document with its own dimensional, material, and testing requirements.
Why Traceability and Certification Matter in Defense Procurement
In defense and aerospace programs, meeting the dimensional requirements of a specification is not enough on its own. It must also be documented that the part does.
Material certifications confirm that the material composition of the washer lot meets the requirements of the applicable standard.
Lot traceability allows the material to be traced back to its origin, including heat number, mill certificate, and manufacturer.
Dimensional inspection records confirm that the part was measured and found to be within the tolerance requirements of the specification.
These documents travel with the parts and are typically retained by the contractor or program for the life of the assembly. Without this documentation, a part may be dimensionally identical to a mil-spec washer but cannot be used in a defense program that requires certified components.
DFARS, CAGE Codes, and ISO 9001: What They Mean for Sourcing
Defense and aerospace buyers commonly look at more than the technical specification when qualifying a supplier. DFARS material compliance, CAGE code registration, and ISO 9001 certification are three of the credentials that come up most often, each covered below.
DFARS Compliance
DFARS stands for Defense Federal Acquisition Regulation Supplement, the set of regulations that governs how the U.S. Department of Defense acquires goods and services.
DFARS material compliance requirements call for certain specialty metals used in defense contracts to be sourced domestically, from the United States or a qualifying country. Specialty metals covered under DFARS include stainless steel, titanium, nickel alloys, cobalt alloys, and zirconium. Common metals such as aluminum, carbon steel, copper, and brass are generally exempt from DFARS specialty metal restrictions.
For washers, DFARS compliance means the raw material, not just the finished part, must meet the domestic sourcing requirements of the applicable clause.
Suppliers manufacturing from DFARS-qualified materials can confirm this compliance as part of their certification documentation. Superior Washer manufactures mil-spec washers from DFARS-qualified materials.
CAGE Codes
CAGE stands for Commercial and Government Entity, a five-character code assigned by the Defense Logistics Agency (DLA) to identify suppliers in the U.S. defense supply chain. A CAGE code is a required identifier for suppliers participating in defense procurement and government contracting.
When a defense contractor or government program specifies a part, the CAGE code of an approved manufacturer may be part of the specification, indicating which manufacturer's part is approved for use.
Suppliers with CAGE codes are registered in the System for Award Management (SAM) and are identifiable in defense procurement databases. Superior Washer holds CAGE codes 1L160 (Hauppauge, NY) and 4WUG7 (Rock Hill, SC).
ISO 9001 Certification
ISO 9001 is an internationally recognized quality management system standard that defines requirements for a quality management system that consistently produces products meeting customer and regulatory requirements.
ISO 9001:2018 certification is increasingly required or preferred in defense and aerospace supply chains as evidence of a supplier's quality system.
Certification is issued by an accredited third-party certification body and requires periodic re-auditing to maintain. Superior Washer is ISO 9001:2018 certified, audited by DNV.
Military Washers from Superior Washer & Gasket
Superior Washer & Gasket Corp. has manufactured washers in the United States since 1972, operating from two facilities in Hauppauge, New York (CAGE 1L160) and Rock Hill, South Carolina (CAGE 4WUG7).
- ISO 9001:2018 certified, audited by DNV
- Manufactures mil-spec washers from DFARS-qualified materials
- Stocks 22 military specifications across the AN, NAS, and MS series
- Certification documentation and material traceability commonly available
- Rush orders accommodated through in-house manufacturing capability across both U.S. facilities
Browse the military washers collection or contact our team to discuss your program requirements.
Sourcing Mil-Spec Washers With Confidence
Mil-spec washers are defined by documentation and traceability, not just dimensions. AN, NAS, and MS represent three distinct standards systems, each commonly associated with specific applications across defense and aerospace programs.
DFARS compliance, CAGE codes, and ISO 9001:2018 certification are among the credentials that matter when qualifying a mil-spec washer supplier.
Superior Washer has stocked and manufactured mil-spec washers from U.S. facilities since 1972. Contact the team or submit an RFQ for program requirements.
Frequently Asked Questions
The following questions address common points of confusion when sourcing military-specification washers.
What is the difference between a mil-spec washer and a commercial washer?
A mil-spec washer is manufactured and certified to a documented standard that defines material, finish, dimensions, and testing requirements, along with supporting documentation such as material certifications and lot traceability. A commercial washer commonly meets dimensional specifications only, without the same certification and traceability requirements.
What does AN, NAS, and MS mean on a washer?
AN stands for Aeronautical Standard, NAS stands for National Aerospace Standard, and MS stands for Military Standard. Each represents a separate standards system commonly applied across different segments of defense and aerospace procurement.
What documentation comes with military-specification washers?
Mil-spec washers are commonly supplied with material certifications, lot traceability records, and dimensional inspection reports confirming the part meets the requirements of its specification.
What is DFARS compliance for washers?
DFARS compliance means the raw material used in a washer, including specialty metals such as stainless steel, titanium, nickel alloys, cobalt alloys, and zirconium, is sourced domestically from the United States or a qualifying country, in accordance with applicable DFARS clauses.
What is a CAGE code and why does it matter for washer sourcing?
A CAGE code is a five-character identifier assigned by the Defense Logistics Agency to suppliers in the U.S. defense supply chain. It is commonly referenced in defense procurement specifications to indicate which manufacturer's part is approved for use.
What is AN960 and where is it used?
AN960 is a general-purpose flat washer and one of the most widely specified mil-spec flat washers in aerospace and defense fastening applications.
What is NAS1149 and how does it differ from AN960?
NAS1149 is a washer governed by the National Aerospace Standard system, commonly specified in aerospace structural fastening applications that call for tighter dimensional tolerances than general-purpose AN washers such as AN960.
Does Superior Washer supply certification documentation with mil-spec washers?
Superior Washer provides certification documentation and material traceability for its mil-spec washer offerings.
Are military washers interchangeable with commercial washers of the same dimensions?
Military washers are typically not considered interchangeable with commercial washers, even when dimensions match, because engineering drawings and program documentation commonly call out the specific mil-spec standard along with its material and certification requirements.
Does Superior Washer accommodate rush orders for mil-spec washers?
Superior Washer accommodates rush orders for mil-spec washers through in-house manufacturing capability across its two U.S. facilities.