The Washer,recessed, cataloged under National Stock Number 5310-01-121-8526, is classified within Federal Supply Class 5310 (Nuts and Washers) of the Hardware and Abrasives group. The manufacturer of record is Leonardo Spa Divisione Sistemi Di Difesa. Government technical data includes 11 specifications, cited from the U.S. Government catalog. The record lists 1 manufacturer part number for this item, enabling identification through both NSN and commercial part number lookups. 5 additional reference documents (drawings, advisory and superseded references) are recorded in the U.S. Government catalog. Current acquisition status: Active.
| Parameter | Value |
|---|---|
| NSN | 5310-01-121-8526 |
| Primary Part Number | 721009663500 |
| Item Name | Washer,recessed |
| FSC / FSG | 5310 / 53 — Nuts and Washers |
| Manufacturer | Leonardo Spa Divisione Sistemi Di Difesa |
| Status | ACTIVE |
| Surface Treatment Document and Classification | QQ-P-416,TY 2,CL 2 FED SPEC SINGLE TREATMENT RESPONSE OVERALL |
| Hardness Rating | 39.0 ROCKWELL C MINIMUM AND 45.0 ROCKWELL C MAXIMUM |
| Style Designator | RECESSED |
| Material Document and Classification | MIL-S-6758 MIL SPEC SINGLE MATERIAL RESPONSE OR MIL-S-18729 MIL SPEC SINGLE MATERIAL RESPONSE OVERALL |
| Outside Diameter | 0.377 INCHES MINIMUM AND 0.387 INCHES MAXIMUM IN |
| Material Thickness | 0.067 INCHES MINIMUM AND 0.069 INCHES MAXIMUM IN |
| Recess Diameter | 0.280 INCHES MINIMUM AND 0.290 INCHES MAXIMUM IN |
| Surface Treatment | CADMIUM AND CHROMATE OVERALL |
| Material | STEEL COMP 4130 OVERALL |
| Hole Diameter | 0.191 INCHES MINIMUM AND 0.195 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 |
|---|---|
| 721009663500 | Leonardo Spa Divisione Sistemi Di Difesa (ITA) |
| Reference | Meaning |
|---|---|
| MS21299-C3 | C/1 Advisory reference — outside the item-of-supply concept Zf Industrieantriebe Witten Gmbh |
| 10109387 | 6/9 Informative reference only Nimikkeistokeskus Ncb Finland |
| 5310PL2130424 | 6/9 Informative reference only Jednolity Indeks Materialowy - Uniform Material Index |
| MS21299C3 | 3/2 Design control — primary reference U.S. Government activity |
| MS21299C3 | 5/9 Secondary reference U.S. Government activity |
NSN 5310-01-121-8526 is a Washer,recessed, manufactured by Leonardo Spa Divisione Sistemi Di Difesa, classified under FSC 5310, Nuts and Washers. Status: active.
NSN 5310-01-121-8526 has 1 manufacturer part number on file: 721009663500 (Leonardo Spa Divisione Sistemi Di Difesa).
Key specifications for 721009663500: Surface Treatment Document and Classification: QQ-P-416,TY 2,CL 2 FED SPEC SINGLE TREATMENT RESPONSE OVERALL; Hardness Rating: 39.0 ROCKWELL C MINIMUM AND 45.0 ROCKWELL C MAXIMUM; Style Designator: RECESSED; Material Document and Classification: MIL-S-6758 MIL SPEC SINGLE MATERIAL RESPONSE OR MIL-S-18729 MIL SPEC SINGLE MATERIAL RESPONSE OVERALL. 11 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.