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S721 ✓ Verified by PartsTable
— · ORING SEAL
WHAT YOU NEED TO KNOW
Material determines chemical compatibility Standard durometer is 70 Shore A
Wrong material = catastrophic seal failure
PRODUCT OVERVIEW

CONNECTOR,RECEPTACLE,ELECTRICAL. Key specifications include material: RUBBER BUTADIENE-ACRYLONITRILE CLASS NBR OVERALL, temp_rating: -65.0 FAHRENHEIT AND 160.0 FAHRENHEIT DEGF, hardness_rating: 68.0 SHORE DUROMETER A NOMINAL OVERALL, center_hole_diameter: 1.103 INCHES MINIMUM AND 1.115 INCHES MAXIMUM IN, cross-sectional_height: 0.135 INCHES MINIMUM AND 0.143 INCHES MAXIMUM IN, cross-sectional_shape_style: O-RING. This product is currently in active production with full OEM support.

This part is cataloged in the Federal Logistics Information System (FLIS) under NSN 5340-00-050-1571, indicating validated use in U.S. government and defense logistics supply chains. Available through authorized enterprise resellers and TPM (Third Party Maintenance) channels.

Verify compatibility with your specific system configuration before ordering.

WHERE IT FITS
S721
NSN: 5340-00-050-1571
FSC: 5340
CAGE: 15434 — CUMMINS INC. (USA)
SPECIFICATIONS
materialRUBBER BUTADIENE-ACRYLONITRILE CLASS NBR OVERALL
temp_rating-65.0 FAHRENHEIT AND 160.0 FAHRENHEIT DEGF
hardness_rating68.0 SHORE DUROMETER A NOMINAL OVERALL
center_hole_diameter1.103 INCHES MINIMUM AND 1.115 INCHES MAXIMUM IN
cross-sectional_height0.135 INCHES MINIMUM AND 0.143 INCHES MAXIMUM IN
cross-sectional_shape_styleO-RING
material_document_and_classificationMIL-P-5516,CL B MIL SPEC SINGLE MATERIAL RESPONSE OVERALL
reference_number_differentiating_characteristicsMATERIAL WILL BE IN ACCORDANCE WITH SHIPS PARTS CONTROL CENTER ACTIVITY HX QUALITY CONTROL,MANUFACTURING AND TESTING SPECIFICATIONS
NSN5340-00-050-1571
COMPONENT DIAGRAM
O-RING / SEAL — MATERIAL DETERMINES APPLICATION ID: — CROSS-SECTION CS: — SPECIFICATION Material: — Durometer: — Temp: — PN: S721 MFR: OEM ⚠ VERIFY BEFORE ORDERING Wrong material = failure. Viton for oil/fuel, EPDM for water/steam, Buna-N for general purpose, Silicone for food-grade. Chemical incompatibility causes swelling, brittleness, or rapid degradation ✓ BROKER TIP Durometer (hardness) affects sealing pressure tolerance. Higher Shore A = harder = higher pressure. Standard durometer is 70A — verify if application requires different hardness PARTSTABLE TECHNICAL DRAWING — NOT TO SCALE
KEY FEATURES
•
MATERIAL: COPPER ALLOY
•
MATERIAL THICKNESS: 0.083 INCHES NOMINAL IN
•
RADIUS: 2.688 INCHES NOMINAL IN
•
OUTSIDE DIAMETER: 1.750 INCHES NOMINAL IN
•
STYLE DESIGNATOR: CONCAVE
TECHNICAL CHARACTERISTICS (FLIS)
MATERIALCOPPER ALLOY
MATERIAL THICKNESS0.083 INCHES NOMINAL IN
RADIUS2.688 INCHES NOMINAL IN
OUTSIDE DIAMETER1.750 INCHES NOMINAL IN
STYLE DESIGNATORCONCAVE
VERIFIED SUBSTITUTES & CROSS-REFERENCES 5
S721Interchangeable
interchangeable cross-reference
interchangeable
J512Interchangeable
interchangeable cross-reference
interchangeable
4479FPC35Interchangeable
interchangeable cross-reference
interchangeable
3279549PC35Interchangeable
interchangeable cross-reference
interchangeable
AN6227-21Interchangeable
interchangeable cross-reference
interchangeable
LIFECYCLE
StatusACTIVE
AvailabilityOEM and secondary market
RoHS CompliantEAR99Not HAZMAT
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FREQUENTLY ASKED QUESTIONS
What is S721?
S721 is a CONNECTOR,RECEPTACLE,ELECTRICAL.
What parts can replace S721?
There are 5 known substitutes for S721: S721, J512, 4479FPC35 and 2 more. Substitute compatibility should be verified for your specific system.
What is the NSN for S721?
S721 is cataloged in the Federal Logistics Information System (FLIS) under NSN 5340-00-050-1571. This indicates validated use in U.S. government and defense supply chains.
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✓ Validated with multiple authoritative sources, including Government, OEM, and Certified sources.
PartsTable Design LLC · partstable.com
Last verified: July 2026