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SIZE55A ✓ 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

CAP-PLUG,PROTECTIVE,DUST AND MOI. Key specifications include material: PLASTIC, length_under_shoulder: 1.000 INCHES NOMINAL IN, open_end_inside_diameter: 3.175 INCHES NOMINAL IN, closed_end_overall_diameter: 2.982 INCHES NOMINAL IN. This product is currently in active production with full OEM support.

This part is cataloged in the Federal Logistics Information System (FLIS) under NSN 5340-00-290-7230, 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
SIZE55A
NSN: 5340-00-290-7230
FSC: 5340
CAGE: 95760 — PROTECTIVE CLOSURES CO INC (USA)
SPECIFICATIONS
materialPLASTIC
length_under_shoulder1.000 INCHES NOMINAL IN
open_end_inside_diameter3.175 INCHES NOMINAL IN
closed_end_overall_diameter2.982 INCHES NOMINAL IN
NSN5340-00-290-7230
COMPONENT DIAGRAM
O-RING / SEAL — MATERIAL DETERMINES APPLICATION ID: — CROSS-SECTION CS: — SPECIFICATION Material: — Durometer: — Temp: — PN: SIZE55A 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: PLASTIC
•
CLOSED END OVERALL DIAMETER: 2.982 INCHES NOMINAL IN
•
LENGTH UNDER SHOULDER: 1.000 INCHES NOMINAL IN
•
OPEN END INSIDE DIAMETER: 3.175 INCHES NOMINAL IN
TECHNICAL CHARACTERISTICS (FLIS)
MATERIALPLASTIC
CLOSED END OVERALL DIAMETER2.982 INCHES NOMINAL IN
LENGTH UNDER SHOULDER1.000 INCHES NOMINAL IN
OPEN END INSIDE DIAMETER3.175 INCHES NOMINAL IN
VERIFIED SUBSTITUTES & CROSS-REFERENCES 23
MILC52078Upgraded Successor
successor cross-reference
successor
RU51089Upgraded Successor
successor cross-reference
successor
28901-17Upgraded Successor
successor cross-reference
successor
21Upgraded Successor
successor cross-reference
successor
MIL-C-5501Upgraded Successor
successor cross-reference
successor
57AUpgraded Successor
successor cross-reference
successor
LIFECYCLE
StatusACTIVE
AvailabilityOEM and secondary market
RoHS CompliantEAR99Not HAZMAT
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FREQUENTLY ASKED QUESTIONS
What is SIZE55A?
SIZE55A is a CAP-PLUG,PROTECTIVE,DUST AND MOI.
What parts can replace SIZE55A?
There are 23 known substitutes for SIZE55A: MILC52078, RU51089, 28901-17 and 20 more. Substitute compatibility should be verified for your specific system.
What is the NSN for SIZE55A?
SIZE55A is cataloged in the Federal Logistics Information System (FLIS) under NSN 5340-00-290-7230. 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