The Seat,valve, cataloged under National Stock Number 4820-00-787-1855, is classified within Federal Supply Class 4820 (Valves, Nonpowered) of the Valves group. The manufacturer of record is Eaton Aerospace, Llc Dba Jackson South. Government technical data includes 6 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through both NSN and commercial part number lookups. 2 additional reference documents (drawings, advisory and superseded references) are recorded in the U.S. Government catalog. Current acquisition status: Active.
| Parameter | Value |
|---|---|
| NSN | 4820-00-787-1855 |
| Primary Part Number | MC5991 |
| Item Name | Seat,valve |
| FSC / FSG | 4820 / 48 — Valves, Nonpowered |
| Manufacturer | Eaton Aerospace, Llc Dba Jackson South |
| Status | ACTIVE |
| Seal Accommodation Type | GROOVED |
| Hardness Rating | 80.5 ROCKWELL C MINIMUM AND 85.0 ROCKWELL C MAXIMUM OVERALL |
| Style Designator | PLAIN |
| Body Inside Diameter | 0.340 INCHES MINIMUM AND 0.472 INCHES MAXIMUM IN |
| Surface Treatment | PASSIVATE OVERALL |
| Material | STEEL COMP 416 OVERALL |
| Acquisition Status | ACTIVE |
| DEMIL Code | DEMIL Q — CCL Item — Commerce Control List |
| Hazard | No hazard code in the DLA record (HMIC N) |
| Criticality Code | X |
| Part Number | Manufacturer |
|---|---|
| MC5991 PRIMARY | Eaton Aerospace, Llc Dba Jackson South (USA) |
| Reference | Meaning |
|---|---|
| 10109263 | 6/9 Informative reference only Nimikkeistokeskus Ncb Finland |
| MC5991 | 5/9 Secondary reference Eaton Aerospace Llc Dba Sterer Engineering Div M.c.aerospace |
NSN 4820-00-787-1855 is a Seat,valve, manufactured by Eaton Aerospace, Llc Dba Jackson South, classified under FSC 4820, Valves, Nonpowered. Status: active.
NSN 4820-00-787-1855 has 1 manufacturer part number on file: MC5991 (Eaton Aerospace, Llc Dba Jackson South).
Key specifications for MC5991: Overall Height: 0.250 INCHES NOMINAL IN; Seal Accommodation Type: GROOVED; Hardness Rating: 80.5 ROCKWELL C MINIMUM AND 85.0 ROCKWELL C MAXIMUM OVERALL; Style Designator: PLAIN. 6 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.
NSN 4820-00-787-1855 has DEMIL Code Q. Demilitarization may be required before disposal or transfer to non-military entities.
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.