PartsTable TECHNICAL DATA SHEET
JULY 2026Technical Data Sheet

51557Cover,respirator

American Optical Co · NSN 4240-01-251-3282 · FSC 4240 · No Item Name Available
Verified by PartsTable
NSN 4240-01-251-3282 — this item is cataloged by the U.S. Government under National Stock Number 4240-01-251-3282. Primary manufacturer part number: 51557.
Features
  • Cover,respirator — FSC 4240
  • Criticality Code Justification: TEXT
  • General Characteristics Item Description: FRONT COVER; SILICONE; W/SET OF 2 SCREWS; SOLE SOURCE REQUIRED BY STATUTE 6.302
  • 4 verified cross-references
  • Primary manufacturer: American Optical Co
Applications
  • Industrial maintenance and repair
  • Government and military logistics
  • Equipment overhaul and refurbishment
General Description

The Cover,respirator, cataloged under National Stock Number 4240-01-251-3282, is classified within Federal Supply Class 4240 (No Item Name Available) of the Fire Fighting, Rescue, and Safety Equipment group. The primary manufacturer of record is American Optical Co. Government technical data includes 2 verified specifications, sourced from the Federal Logistics Information System (FLIS). This item has 4 commercial cross-references from 4 manufacturers, enabling identification through both NSN and commercial part number lookups. 5 verified substitutes exist in the FLIS interchangeability database. Current acquisition status: Active.

Technical Specifications
ParameterValue
NSN4240-01-251-3282
Primary Part Number51557
Item NameCover,respirator
FSC / FSG4240 / 42 — No Item Name Available
ManufacturerAmerican Optical Co
StatusACTIVE
Criticality Code JustificationTEXT
General Characteristics Item DescriptionFRONT COVER; SILICONE; W/SET OF 2 SCREWS; SOLE SOURCE REQUIRED BY STATUTE 6.302
Lifecycle & Compliance
Acquisition StatusACTIVE
HAZMATNo
Verified Substitutes 5
3120-00-356-3499SC-B-69877 INTERCHANGEABLE
Bearing,sleeve
Us Army Communications & Electronics Materiel Readiness Command Logistics Engineering Dir
5962-00-455-0843911411-9 INTERCHANGEABLE
Microcircuit,linear
Bae Systems Information and Electronic Systems Integration Inc.
5310-00-551-6680515-57 INTERCHANGEABLE
Washer,flat
Undersea Sensor Systems Inc Div Ultra Sonobuoy Systems
6685-01-259-6098167218 INTERCHANGEABLE
Gage,compound Pressure-Vacuum,di
Ametek, Inc. Div Aerospace & Defense
2530-01-326-3069 INTERCHANGEABLE
Brake Shoe
Cross-Reference Index
Part NumberManufacturer
51557 American Optical Co (USA)
51557 Aearo Company 1 Dba Aearo Div Ao Safety Occupational Prescription Eyewear (USA)
51557 3m Company (USA)
51557 Aearo Company (USA)
Related Parts
3120-00-356-3499INTERCHANGEABLE
BEARING,SLEEVE
SC-B-69877
5962-00-455-0843INTERCHANGEABLE
MICROCIRCUIT,LINEAR
911411-9
5310-00-551-6680INTERCHANGEABLE
WASHER,FLAT
515-57
6685-01-259-6098INTERCHANGEABLE
GAGE,COMPOUND PRESSURE-VACUUM,DI
167218
2530-01-326-3069INTERCHANGEABLE
BRAKE SHOE

Frequently Asked Questions

What is NSN 4240-01-251-3282?

NSN 4240-01-251-3282 is a Cover,respirator, manufactured by American Optical Co, classified under FSC 4240 (No Item Name Available). Status: active.

What are the part numbers for NSN 4240-01-251-3282?

NSN 4240-01-251-3282 has 4 cross-referenced part numbers: 51557 (American Optical Co), 51557 (Aearo Company 1 Dba Aearo Div Ao Safety Occupational Prescription Eyewear), 51557 (3m Company), 51557 (Aearo Company).

What NSN replaces 4240-01-251-3282?

There are 5 known substitutes for 4240-01-251-3282: 3120-00-356-3499, 5962-00-455-0843, 5310-00-551-6680 and 2 more. Verify interchangeability with system specifications before substitution.

What are the specifications of 51557?

Key specifications for 51557: Criticality Code Justification: TEXT; General Characteristics Item Description: FRONT COVER; SILICONE; W/SET OF 2 SCREWS; SOLE SOURCE REQUIRED BY STATUTE 6.302; End Item Identification: AMERICAN OPTICAL MODEL 7 STAR S7800 SERIES RESPIRATOR. 3 total characteristics are documented in the Federal Logistics Information System.

Validated with multiple authoritative sources, including Government, OEM, and Certified sources.
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