PartsTable TECHNICAL DATA SHEET
JULY 2026Technical Data Sheet

579 .75 FOCALLens,helmet,welder's

American Optical Co · NSN 4240-01-220-2940 · FSC 4240 · No Item Name Available
Verified by PartsTable
NSN 4240-01-220-2940 — this item is cataloged by the U.S. Government under National Stock Number 4240-01-220-2940. Primary manufacturer part number: 579 .75 FOCAL.
Features
  • Lens,helmet,welder's — FSC 4240
  • Material: PLASTIC
  • 7 verified cross-references
  • Primary manufacturer: American Optical Co
Applications
  • Applications requiring Plastic construction
General Description

The Lens,helmet,welder's, cataloged under National Stock Number 4240-01-220-2940, 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 1 verified specification, sourced from the Federal Logistics Information System (FLIS). This item has 7 commercial cross-references from 4 manufacturers, enabling identification through both NSN and commercial part number lookups. 12 verified substitutes exist in the FLIS interchangeability database. Current acquisition status: Cancelled.

Technical Specifications
ParameterValue
NSN4240-01-220-2940
Primary Part Number579 .75 FOCAL
Item NameLens,helmet,welder's
FSC / FSG4240 / 42 — No Item Name Available
ManufacturerAmerican Optical Co
StatusCANCELLED
MaterialPLASTIC
Lifecycle & Compliance
Acquisition StatusCANCELLED
HAZMATNo
Verified Substitutes 12
9540-00-145-8392 INTERCHANGEABLE
Angle,structural
3110-00-156-47131248P INTERCHANGEABLE
Bearing,ball,annular
Curtiss-Wright Electro-Mechanical Corporation Div Epd
5330-00-285-946249362 INTERCHANGEABLE
Seal,plain Encased
Dana Automotive Systems Group, Llc Dba Dana Sealing Products
5930-00-599-9188153C5841P1 INTERCHANGEABLE
Switch,thermostatic
Bae Systems Controls Inc.
5999-01-075-7550MP-2 INTERCHANGEABLE
Mounting Pad,electrical-Electron
Vector Electronics & Technology Inc
5985-01-174-258575Z-2G-BNC INTERCHANGEABLE
Attenuator,fixed
Jfw Industries Incorporated Dba Jfw Industries Inc
6250-01-246-5424M175 INTERCHANGEABLE
Lock,fluorescent Lamp
Mcgill Mfg Co Inc Electrical Div
6540-01-274-7165 INTERCHANGEABLE
Lens,ophthalmic,sphere
6625-01-349-0467MP-2 INTERCHANGEABLE
Generator,pulse
Thermo Eberline Llc Dba Thermo Fisher Scientific Div Thermo Fisher Scientific
6210-01-475-6589CHL175MR3DLG120CWASFLPI INTERCHANGEABLE
Light Fixture,roadw
Lithonia Lighting National Services Industries Inc Div
Cross-Reference Index
Part NumberManufacturer
579 .75 FOCAL American Optical Co (USA)
579 .75 FOCAL Aearo Company (USA)
579.75 FOCAL Aearo Company 1 Dba Aearo Div Ao Safety Occupational Prescription Eyewear (USA)
M175 Kedman Co (USA)
44970 .75 FOCAL Aearo Company (USA)
44970 .75 FOCAL American Optical Co (USA)
MP-2 Kedman Co (USA)
Related Parts
9540-00-145-8392INTERCHANGEABLE
ANGLE,STRUCTURAL
3110-00-156-4713INTERCHANGEABLE
BEARING,BALL,ANNULAR
1248P
5330-00-285-9462INTERCHANGEABLE
SEAL,PLAIN ENCASED
49362
5930-00-599-9188INTERCHANGEABLE
SWITCH,THERMOSTATIC
153C5841P1
5999-01-075-7550INTERCHANGEABLE
MOUNTING PAD,ELECTRICAL-ELECTRON
MP-2
5985-01-174-2585INTERCHANGEABLE
ATTENUATOR,FIXED
75Z-2G-BNC
6250-01-246-5424INTERCHANGEABLE
LOCK,FLUORESCENT LAMP
M175
6540-01-274-7165INTERCHANGEABLE
LENS,OPHTHALMIC,SPHERE
6625-01-349-0467INTERCHANGEABLE
GENERATOR,PULSE
MP-2
6210-01-475-6589INTERCHANGEABLE
LIGHT FIXTURE,ROADW
CHL175MR3DLG120CWASFLPI
6605-01-527-8592INTERCHANGEABLE
PLOTTER-PROTRACTOR,AIR NAVIGATIO
MP-2
7025-01-555-8375INTERCHANGEABLE
PROCESSOR,GATEWAY
MP2

Frequently Asked Questions

What is NSN 4240-01-220-2940?

NSN 4240-01-220-2940 is a Lens,helmet,welder's, manufactured by American Optical Co, classified under FSC 4240 (No Item Name Available). Status: cancelled.

What are the part numbers for NSN 4240-01-220-2940?

NSN 4240-01-220-2940 has 7 cross-referenced part numbers: 579 .75 FOCAL (American Optical Co), 579 .75 FOCAL (Aearo Company), 579.75 FOCAL (Aearo Company 1 Dba Aearo Div Ao Safety Occupational Prescription Eyewear), M175 (Kedman Co), 44970 .75 FOCAL (Aearo Company) and 2 more.

What NSN replaces 4240-01-220-2940?

There are 12 known substitutes for 4240-01-220-2940: 9540-00-145-8392, 3110-00-156-4713, 5330-00-285-9462 and 9 more. Verify interchangeability with system specifications before substitution.

What are the specifications of 579 .75 FOCAL?

Key specifications for 579 .75 FOCAL: Material: PLASTIC; Special Features: 1.750 FOCAL POWER FOR AGE 50 TO 52; MAGNIFYING LENS; Overall Width: 2.000 INCHES NOMINAL IN; Overall Length: 4.000 INCHES NOMINAL IN. 4 total characteristics are documented in the Federal Logistics Information System.

Is NSN 4240-01-220-2940 still in active supply?

NSN 4240-01-220-2940 is currently cancelled. Check with the Defense Logistics Agency for current availability and authorized substitutes.

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