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Technical Data Sheet
PartsTable / COMPONENT / MS21921-4W
MS21921-4W ✓ Verified by PartsTable
— · HOSE FITTING
WHAT YOU NEED TO KNOW
PTFE tape on tapered threads (NPT/BSPT) JIC/AN flare connections seal metal-to-metal — no tape
NPT != BSPT — look identical, NOT interchangeable
PRODUCT OVERVIEW

The INJECTOR ASSEMBLY,FUEL is a the manufacturer industrial component. Key specifications include material: ALUMINUM ALLOY OVERALL, nut_style: TUBE COUPLING, nut_height: 0.72 INCHES NOMINAL IN, seat_angle: 45.0 DEGREES NOMINAL, thread_class: 3B, thread_series: UNIFIED NATIONAL JOINT FINE (UNJF). This product is currently in active production with full OEM support.

This part is cataloged in the Federal Logistics Information System (FLIS) under NSN 4730-00-222-8636, 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
MS21921-4W
NSN: 4730-00-222-8636
FSC: 4730
CAGE: 96906 — MILITARY STANDARDS PROMULGATED BY MILITARY DEPARTMENTS UNDER AUTHORITY OF DEFENSE STANDARDIZATION MANUAL 4120 3-M
SPECIFICATIONS
materialALUMINUM ALLOY OVERALL
nut_styleTUBE COUPLING
nut_height0.72 INCHES NOMINAL IN
seat_angle45.0 DEGREES NOMINAL
thread_class3B
thread_seriesUNIFIED NATIONAL JOINT FINE (UNJF)
thread_directionRIGHT-HAND
width_across_flats0.558 INCHES MINIMUM AND 0.565 INCHES MAXIMUM IN
nominal_thread_size0.4375 INCHES IN
end_item_identificationPSP BLK20 A K
smallest_inside_diameter0.300 INCHES MINIMUM AND 0.305 INCHES MAXIMUM IN
thread_quantity_per_inch20.0
NSN4730-00-222-8636
COMPONENT DIAGRAM
HOSE FITTING — THREAD TYPE IS CRITICAL END A: — STRAIGHT END B: — SPECIFICATIONS Thread: — Material: — Pressure: — PN: MS21921-4W · OEM ⚠ VERIFY BEFORE ORDERING NPT ≠ BSPT — tapered threads look identical but are NOT interchangeable. Wrong thread = leak. JIC (37°) ≠ AN (37°) ≠ SAE 45° — flare angles must match exactly. Measure thread pitch with gauge — visual identification is unreliable ✓ BROKER TIP Always use thread sealant (PTFE tape or pipe compound) on tapered threads (NPT/BSPT). JIC/AN flare fittings seal metal-to-metal — never use tape on flare connections PARTSTABLE TECHNICAL DRAWING — NOT TO SCALE
KEY FEATURES
•
MATERIAL: ALUMINUM ALLOY 7075 OVERALL
•
SEAT ANGLE: 45.00 DEGREES NOMINAL
•
NUT HEIGHT: 0.719 INCHES NOMINAL IN
•
THREAD QUANTITY PER INCH: 20
•
SURFACE TREATMENT: ANODIZE OVERALL
•
NOMINAL TUBE OUTSIDE DIAMETER: 0.250 INCHES IN
•
LENGTH TO SHOULDER: 0.547 INCHES NOMINAL IN
•
NOMINAL THREAD SIZE: 0.438 INCHES IN
TECHNICAL CHARACTERISTICS (FLIS)
MATERIALALUMINUM ALLOY 7075 OVERALL
SEAT ANGLE45.00 DEGREES NOMINAL
NUT HEIGHT0.719 INCHES NOMINAL IN
THREAD QUANTITY PER INCH20
SURFACE TREATMENTANODIZE OVERALL
NOMINAL TUBE OUTSIDE DIAMETER0.250 INCHES IN
LENGTH TO SHOULDER0.547 INCHES NOMINAL IN
NOMINAL THREAD SIZE0.438 INCHES IN
NUT STYLETUBE COUPLING
SMALLEST INSIDE DIAMETER0.300 INCHES NOMINAL IN
VERIFIED SUBSTITUTES & CROSS-REFERENCES 12
MS21921-4Interchangeable
interchangeable cross-reference
interchangeable
4730-554-8015Interchangeable
interchangeable cross-reference
interchangeable
4730005548015Interchangeable
interchangeable cross-reference
interchangeable
AS21921-4DInterchangeable
interchangeable cross-reference
interchangeable
AS18280Interchangeable
interchangeable cross-reference
interchangeable
MS21921-4DInterchangeable
interchangeable cross-reference
interchangeable
LIFECYCLE
StatusACTIVE
AvailabilityOEM and secondary market
RoHS CompliantEAR99Not HAZMAT
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FREQUENTLY ASKED QUESTIONS
What is MS21921-4W?
MS21921-4W is a INJECTOR ASSEMBLY,FUEL.
What parts can replace MS21921-4W?
There are 12 known substitutes for MS21921-4W: MS21921-4, 4730-554-8015, 4730005548015 and 9 more. Substitute compatibility should be verified for your specific system.
What is the NSN for MS21921-4W?
MS21921-4W is cataloged in the Federal Logistics Information System (FLIS) under NSN 4730-00-222-8636. 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