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BK21 — HOLDER,ELECTRICAL CONTACT BRUSH

✓ Government record, cited
— · ORING SEAL
PRODUCT OVERVIEW

BK21: HOLDER,ELECTRICAL CONTACT BRUSH.

HOLDER,ELECTRICAL CONTACT BRUSH. Key specifications include material: RUBBER BUTADIENE-ACRYLONITRILE CLASS NBR, center_hole_diameter: 17.680 INCHES MINIMUM AND 17.770 INCHES MAXIMUM IN, cross-sectional_height: 0.269 INCHES MINIMUM AND 0.281 INCHES MAXIMUM IN. This part is cataloged in the U.S.

Government catalog under NSN 5331-00-810-9658, 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
BK21
NSN: 5331-00-810-9658
NIINs: 008109658, 011088937, 013164485
FSC: 5331 — O-ring
CAGE: 63857 — CIRCOR NAVAL SOLUTIONS LLC DBA WARREN PUMPS (USA)
SPECIFICATIONS
materialRUBBER BUTADIENE-ACRYLONITRILE CLASS NBR
center_hole_diameter17.680 INCHES MINIMUM AND 17.770 INCHES MAXIMUM IN
cross-sectional_height0.269 INCHES MINIMUM AND 0.281 INCHES MAXIMUM IN
NSN5331-00-810-9658
COMPONENT DIAGRAM
O-RING / SEAL — MATERIAL DETERMINES APPLICATION ID: — CROSS-SECTION CS: — SPECIFICATION Material: — Durometer: — Temp: — PN: BK21 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
•
CROSS-SECTIONAL HEIGHT: 0.269 INCHES MINIMUM AND 0.281 INCHES MAXIMUM IN
•
CENTER HOLE DIAMETER: 17.680 INCHES MINIMUM AND 17.770 INCHES MAXIMUM IN
•
MATERIAL: RUBBER BUTADIENE-ACRYLONITRILE CLASS NBR
TECHNICAL CHARACTERISTICS
CROSS-SECTIONAL HEIGHT0.269 INCHES MINIMUM AND 0.281 INCHES MAXIMUM IN
CENTER HOLE DIAMETER17.680 INCHES MINIMUM AND 17.770 INCHES MAXIMUM IN
MATERIALRUBBER BUTADIENE-ACRYLONITRILE CLASS NBR
SUBSTITUTES & CROSS-REFERENCES 2
R738PC11Same NSN cross-reference
Same NSN cross-reference
Also cataloged under this NSN
R737PC47Same NSN cross-reference
Same NSN cross-reference
Also cataloged under this NSN
LIFECYCLE
NSN statusCancelled· U.S. Government catalog
Shelf-life managedAcquisition advice: Terminal item — stock exhausted; no further procurementNo demilitarization required
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FREQUENTLY ASKED QUESTIONS
What is BK21?
BK21 is a HOLDER,ELECTRICAL CONTACT BRUSH.
What parts can replace BK21?
There are 2 known substitutes for BK21: R738PC11, R737PC47. Substitute compatibility should be verified for your specific system.
What is the NSN for BK21?
BK21 is cataloged in the U.S. Government catalog under NSN 5331-00-810-9658. This indicates validated use in U.S. government and defense supply chains.
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✓ PartsTable — the parts reference. Every fact cited to its source.
PartsTable Design LLC · partstable.com
U.S. Government catalog: edition PUBLOGDVD v12.0.0 (OCT 2026), edition date 2026-10-01, retrieved 2026-10-18.
PartsTable commercial catalog: edition Unified commercial catalog snapshot through 2026-09-28, edition date not on file, retrieved 2026-09-28.