PartsTable TECHNICAL DATA SHEET
JULY 2026Technical Data Sheet

MS9021D-020O-Ring

Military Standards Promulgated by Military Departments Under Authority of Defense Standardization Manual 4120 3-M · NSN 5331-01-388-3987 · FSC 5331 · O-Ring
Verified by PartsTable
NSN 5331-01-388-3987 — this item is cataloged by the U.S. Government under National Stock Number 5331-01-388-3987. Primary manufacturer part number: MS9021D-020.
Features
  • O-Ring — FSC 5331
  • Material Document and Classification: AMS7271-80 ASSN STD SINGLE MATERIAL RESPONSE
  • Center Hole Diameter: 0.858 INCHES MINIMUM AND 0.870 INCHES MAXIMUM IN
  • Material: RUBBER BUTADIENE-ACRYLONITRILE CLASS NBR
  • Cross-Sectional Height: 0.067 INCHES MINIMUM AND 0.073 INCHES MAXIMUM IN
  • 4 verified cross-references
  • Primary manufacturer: Military Standards Promulgated by Military Departments Under Authority of Defense Standardization Manual 4120 3-M
Applications
  • Fluid containment and leak prevention
  • Pressure boundary maintenance
  • Environmental sealing
  • Applications requiring Rubber Butadiene-Acrylonitrile Class Nbr construction
General Description

The O-Ring, cataloged under National Stock Number 5331-01-388-3987, is classified within Federal Supply Class 5331 (O-Ring) of the Hardware and Abrasives group. The primary manufacturer of record is Military Standards Promulgated by Military Departments Under Authority of Defense Standardization Manual 4120 3-M. Government technical data includes 4 verified specifications, sourced from the Federal Logistics Information System (FLIS). This item has 4 commercial cross-references from 3 manufacturers, enabling identification through both NSN and commercial part number lookups. 2 verified substitutes exist in the FLIS interchangeability database. Current acquisition status: Active.

Technical Specifications
ParameterValue
NSN5331-01-388-3987
Primary Part NumberMS9021D-020
Item NameO-Ring
FSC / FSG5331 / 53 — O-Ring
ManufacturerMilitary Standards Promulgated by Military Departments Under Authority of Defense Standardization Manual 4120 3-M
StatusACTIVE
Material Document and ClassificationAMS7271-80 ASSN STD SINGLE MATERIAL RESPONSE
Center Hole Diameter0.858 INCHES MINIMUM AND 0.870 INCHES MAXIMUM IN
MaterialRUBBER BUTADIENE-ACRYLONITRILE CLASS NBR
Cross-Sectional Height0.067 INCHES MINIMUM AND 0.073 INCHES MAXIMUM IN
Lifecycle & Compliance
Acquisition StatusACTIVE
HAZMATNo
Verified Substitutes 2
5331-00-551-8250AS3578-020 INTERCHANGEABLE
O-Ring
Sae International Dba Sae International
5331-01-015-3371AS568-020 INTERCHANGEABLE
O-Ring
Sae International Dba Sae International
Cross-Reference Index
Part NumberManufacturer
MS9021D-020 Military Standards Promulgated by Military Departments Under Authority of Defense Standardization Manual 4120 3-M
AS3578-020 Military Standards Promulgated by Military Departments Under Authority of Defense Standardization Manual 4120 3-M
MS9021-020 Zf Industrieantriebe Witten Gmbh (DEU)
SAE-AS3578 Sae International Dba Sae International (USA)
Related Parts
5331-00-551-8250INTERCHANGEABLE
O-RING
AS3578-020
5331-01-015-3371INTERCHANGEABLE
O-RING
AS568-020

Frequently Asked Questions

What is NSN 5331-01-388-3987?

NSN 5331-01-388-3987 is a O-Ring, manufactured by Military Standards Promulgated by Military Departments Under Authority of Defense Standardization Manual 4120 3-M, classified under FSC 5331 (O-Ring). Status: active.

What are the part numbers for NSN 5331-01-388-3987?

NSN 5331-01-388-3987 has 4 cross-referenced part numbers: MS9021D-020 (Military Standards Promulgated by Military Departments Under Authority of Defense Standardization Manual 4120 3-M), AS3578-020 (Military Standards Promulgated by Military Departments Under Authority of Defense Standardization Manual 4120 3-M), MS9021-020 (Zf Industrieantriebe Witten Gmbh), SAE-AS3578 (Sae International Dba Sae International).

What NSN replaces 5331-01-388-3987?

There are 2 known substitutes for 5331-01-388-3987: 5331-00-551-8250, 5331-01-015-3371. Verify interchangeability with system specifications before substitution.

What are the specifications of MS9021D-020?

Key specifications for MS9021D-020: Material Document and Classification: AMS7271-80 ASSN STD SINGLE MATERIAL RESPONSE; Center Hole Diameter: 0.858 INCHES MINIMUM AND 0.870 INCHES MAXIMUM IN; Material: RUBBER BUTADIENE-ACRYLONITRILE CLASS NBR; Cross-Sectional Height: 0.067 INCHES MINIMUM AND 0.073 INCHES MAXIMUM IN. 4 total characteristics are documented in the Federal Logistics Information System.

Validated with multiple authoritative sources, including Government, OEM, and Certified sources.
PartsTable Design LLC · partstable.com