The Washer,recessed, cataloged under National Stock Number 5310-01-288-1256, is classified within Federal Supply Class 5310 (Nuts and Washers) of the Hardware and Abrasives group. The manufacturer of record is Anillo Industries Llc. Government technical data includes 9 specifications, cited from the U.S. Government catalog. The record lists 2 manufacturer part numbers for this item, enabling identification through both NSN and commercial part number lookups. 1 additional reference document (drawings, advisory and superseded references) is recorded in the U.S. Government catalog. 3 items share a part number with this NSN in the catalog (possible match — not a government interchangeability claim). Current acquisition status: Active.
| Parameter | Value |
|---|---|
| NSN | 5310-01-288-1256 |
| Primary Part Number | AS21-4 |
| Item Name | Washer,recessed |
| FSC / FSG | 5310 / 53 — Nuts and Washers |
| Manufacturer | Anillo Industries Llc |
| Status | ACTIVE |
| Hardness Rating | 24.0 ROCKWELL C MINIMUM AND 37.0 ROCKWELL C MAXIMUM |
| Style Designator | RECESSED |
| Material Document and Classification | AMS 5525 ASSN STD SINGLE MATERIAL RESPONSE OR AMS 5732 ASSN STD SINGLE MATERIAL RESPONSE OVERALL |
| Outside Diameter | 0.521 INCHES MINIMUM AND 0.541 INCHES MAXIMUM IN |
| Material Thickness | 0.064 INCHES MINIMUM AND 0.080 INCHES MAXIMUM IN |
| Recess Diameter | 0.334 INCHES MINIMUM AND 0.344 INCHES MAXIMUM IN |
| Material | IRON ALLOY 660 OVERALL |
| Hole Diameter | 0.252 INCHES MINIMUM AND 0.260 INCHES MAXIMUM IN |
| Recess Angle | 90.0 DEGREES NOMINAL |
| Acquisition Status | ACTIVE |
| DEMIL Code | DEMIL A — No Demilitarization Required |
| Hazard | No hazard code in the DLA record (HMIC N) |
| Criticality Code | X |
| Part Number | Manufacturer |
|---|---|
| AS21-4 PRIMARY | Anillo Industries Llc (USA) |
| 88-50001-002 | Raytheon Company (USA) |
| Reference | Meaning |
|---|---|
| 88-50001-002 | 5/9 Secondary reference Hughes Missile Systems Co San Diego |
NSN 5310-01-288-1256 is a Washer,recessed, manufactured by Anillo Industries Llc, classified under FSC 5310, Nuts and Washers. Status: active.
NSN 5310-01-288-1256 has 2 manufacturer part numbers on file: AS21-4 (Anillo Industries Llc), 88-50001-002 (Raytheon Company).
3 possible matches (shared part number, not a government interchangeability claim): 4720-01-358-8542, 4720-01-358-8543, 4720-01-358-8545. Verify interchangeability with system specifications before substitution.
Key specifications for AS21-4: Hardness Rating: 24.0 ROCKWELL C MINIMUM AND 37.0 ROCKWELL C MAXIMUM; Style Designator: RECESSED; Material Document and Classification: AMS 5525 ASSN STD SINGLE MATERIAL RESPONSE OR AMS 5732 ASSN STD SINGLE MATERIAL RESPONSE OVERALL; Outside Diameter: 0.521 INCHES MINIMUM AND 0.541 INCHES MAXIMUM IN. 9 specifications are documented in the U.S. Government catalog.
No hazard code in the DLA record (HMIC N). Hazard information on this page is shown exactly as it appears in the DLA record.
U.S. Government catalog: edition PUBLOGDVD v12.0.0 (OCT 2026), edition date 2026-10-01, retrieved 2026-10-16.
U.S. Government catalog: edition PUBLOGDVD v12.0.0 (OCT 2026), edition date 2026-10-01, retrieved 2026-10-18.