Mil-spec part number, MS28775 family
MS28775-021 O-ring: nitrile (NBR), AS568-021 nominal size
MS28775-021 has the AS568-021 nominal size, 0.926 in (23.52 mm) inside diameter by 0.070 in (1.78 mm) cross-section, in nitrile (NBR) procured to MIL-PRF-25732 (MS28775 part drawing). The DLA ASSIST and SAE Mobilus records read: Inactive (MIL-PRF-25732); AS28775A current (revised 2008, reaffirmed 2025). The same part is also printed as AS28775-021. Its DoD sheet, MS28775, holds the inside-diameter tolerance tighter than AS568 above 0.500 in ID, and the document sets the compound, so an AS568-021 ring is not the same part as MS28775-021. Send the designator exactly as the print reads and we quote it against that document.
- Inside diameter
- 0.926 in23.52 mm; tolerance per the MS28775 sheet
- Cross-section
- 0.070 in1.78 mm, +/- 0.003 in
- AS568 nominal size
- AS568-0210xx series
- Document status
- InactiveMIL-P-25732 / MIL-PRF-25732
Part facts
| Item | Value |
|---|---|
| Part number | MS28775-021; also printed as AS28775-021 |
| NSN | 5331-01-213-8344 and 5331-01-160-2085 (DLA FLIS lists this part number on each; read 2026-10-08) |
| Stock | In stock in Orange, CA |
| Procured to | MIL-PRF-25732 (MS28775 part drawing) |
| Size sheet | MS28775 Revision E (1984-03-23), the DoD drawing; canceled on 2000-09-29 and superseded by SAE-AS28775 with the same part numbers |
| SAE document | SAE AS28775 |
| Status | Inactive (MIL-PRF-25732); AS28775A current (revised 2008, reaffirmed 2025) |
| Base polymer | Nitrile (NBR) |
| AS568 nominal size | AS568-021 |
| CAD for the AS568-021 nominal size | AS568-021 STEP 3D solid, AS568-021 DXF 2D drawing, AS568-021 PDF dimensioned drawing; generated from the AS568 nominal dimensions, so verify against your drawing |
| Back-up rings | MS28774-021 (single-turn scarf-cut PTFE) or MS27595-021 (continuous PTFE), both procured to SAE AS8791; both drawings are inactive for new design |
| Dimension | Value | Tolerance |
|---|---|---|
| Inside diameter (ID) | 0.926 in 23.52 mm | tighter than AS568 above 0.500 in ID; see the MS28775 sheet |
| Cross-section (W) | 0.070 in 1.78 mm | +/- 0.003 in (0.08 mm) |
| Outside diameter (reference) | 1.066 in 27.08 mm | derived: ID + 2 x W |
Millimeter values are converted from the inch table. The MS28775 sheet holds the inside-diameter tolerance tighter than AS568 above 0.500 in ID; the drawing governs. The MS28775 sheet's note 1 says this size is intended only for use as a static seal, not in applications with reciprocating or rotary movement.
Same nominal size, other documents
Other part numbers for the AS568-021 size
These part numbers name the AS568-021 nominal size under a different document, so each one is a different compound. They are not interchangeable with MS28775-021 unless the print or the buyer's engineering allows it. At this size the family sheets for MS29513-021 and AS9386-021 hold a tighter inside-diameter tolerance than AS568.
| Part number | Document | Polymer | Status |
|---|---|---|---|
| M83461/1-021 | MIL-P-83461/1 | NBR | Canceled; AS83461/1C current |
| M83248/1-021 | MIL-R-83248/1 (Class 1) | FKM | Canceled; AS3209C stabilized; AS83248/1A current |
| M83248/2-021 | MIL-R-83248/2 (Class 2) | FKM | Canceled; AS3581A stabilized; AS83248/2A current |
| AS3209-021 | SAE AS3209 (AMS7276) | FKM | AS3209C stabilized |
| M83485/1-021 | MIL-R-83485 | FKM, low-temperature grade | Canceled |
| M25988/1-021 | MIL-DTL-25988/1 | FVMQ | Active |
| M25988/2-021 | MIL-DTL-25988/2 | FVMQ | Active |
| M25988/3-021 | MIL-DTL-25988/3 | FVMQ | Active |
| M25988/4-021 | MIL-DTL-25988/4 | FVMQ | Active |
| MS29513-021 | MIL-P-5315 (MS29513 part drawing) | NBR | Canceled (MIL-P-5315); AS29513C current |
| AS3582-021 | SAE AS3582 (AMS3304) | VMQ silicone | AS3582 current |
| AS9386-021 | SAE AS9386 (AMS7267) | VMQ silicone | AS9386B current |
The base polymer
MS28775-021 is nitrile (NBR). For the MIL-PRF-25732 family the MIL title and the SAE title print different upper limits, so this page quotes no temperature figure; the governing document and the compound sheet for the qualified grade decide it.
Material page: Nitrile (NBR) O-rings. Every document in the family: MS28775 O-rings.
Nearby MS28775 part numbers
| Part number | ID in | ID mm | W in | W mm |
|---|---|---|---|---|
| MS28775-018 | 0.739 | 18.77 | 0.070 | 1.78 |
| MS28775-019 | 0.801 | 20.35 | 0.070 | 1.78 |
| MS28775-020 | 0.864 | 21.95 | 0.070 | 1.78 |
| MS28775-021 | 0.926 | 23.52 | 0.070 | 1.78 |
| MS28775-022 | 0.989 | 25.12 | 0.070 | 1.78 |
| MS28775-023 | 1.051 | 26.70 | 0.070 | 1.78 |
| MS28775-024 | 1.114 | 28.30 | 0.070 | 1.78 |
Frequently asked
What is the AS568 nominal size of MS28775-021?
MS28775-021 has the AS568-021 nominal size: 0.926 in (23.52 mm) inside diameter by 0.070 in (1.78 mm) cross-section. The MS28775 sheet holds the inside-diameter tolerance tighter than AS568 above 0.500 in ID, and MIL-PRF-25732 (MS28775 part drawing) sets the nitrile (NBR) compound. An AS568-021 ring shares the nominal size but not the tolerance, so it is not the same part as MS28775-021.
What is the NSN for MS28775-021?
DLA's public FLIS data lists MS28775-021 on NSNs 5331-01-213-8344 and 5331-01-160-2085 (read 2026-10-08). An NSN is the federal catalog's number for the item; your contract or print decides what is ordered.
Is MIL-P-25732 / MIL-PRF-25732 still active?
The DLA ASSIST and SAE Mobilus records read: Inactive (MIL-PRF-25732); AS28775A current (revised 2008, reaffirmed 2025). The first status is the material document's: MIL-PRF-25732 is inactive for new design (MIL-P-25732C Notice 1, 1989-11-15). The second is SAE-AS28775's, the SAE part standard that superseded the MS28775 drawing when DoD canceled the drawing on 2000-09-29; the cancellation notice keeps the part numbers unchanged. Both come from the DLA ASSIST and SAE Mobilus records listed under Sources, with the date each was read. A canceled or inactive MIL document can still be the one a print calls out, and your print decides which you order to. The MS28775 sheet's note 1 says this size is intended only for use as a static seal, not in applications with reciprocating or rotary movement.
How do I order MS28775-021?
Send the designator exactly as the print reads, with its revision, any suffix letter, the quantity and the paperwork the order needs. MS28775-021 is quoted and supplied against MIL-PRF-25732 (MS28775 part drawing) or SAE AS28775, in the compound the print calls out, with a certificate of conformance with every order. When the print calls out a QPL-listed specification, the finished molded O-ring, or the material it is molded from, comes from a manufacturer listed on that QPL; Conquest supplies it and is not itself on any QPL. A Conquest representative replies within one business day.
Sources
DLA ASSIST document details, ident 18115 (MIL-PRF-25732), read 2026-09-24; DLA ASSIST: MIL-P-25732C Notice 1 (1989-11-15, inactive for new design), the MS28775 record with MS28775E Notice 3 (cancellation, 2000-09-29) and the QPL-25732 record, read 2026-09-25; SAE Mobilus: AS28775A (revised December 2008, reaffirmed 2025-02-08), read 2026-09-25; AMSP25732A (cancelled August 2003), current-revision record read 2026-09-27; DLA ASSIST: MIL-P-83461/1 (ident 33814, read 2026-09-24), SAE-AMS-P-83461/1 (ident 213939) and SAE-AS83461/1 (ident 277052), read 2026-09-25, for the M83461/1 successor chain; SAE Mobilus: AS83461/1C (revised October 2016, reaffirmed 2021-11-08) and AMSP83461 (issued 1998-04-01), current-revision records read 2026-09-27; DLA ASSIST: the MS28775E sheet (1984-03-23, 7 sheets) with Notice 1 (1989-11-15), Notice 2 (2000-08-18) and Notice 3 (2000-09-29), ident 41724, read 2026-10-04, for the dash-to-size mapping, the tolerance note and the size notes; the NSNs from DLA's public FLIS data (PUB LOG Reference, Identification and Characteristics files, updated 2026-10-01, read 2026-10-08); an NSN is the federal catalog's stock number for an item and does not name or approve a supplier; AS568 nominal dimensions from the Parker O-Ring Handbook ORD 5700, 2021 printing, section IX, AS568 size tables (Series 2-XXX and 3-XXX), pages 9-2 to 9-11, read 2026-10-13; the dash-to-size mapping, the size notes and the tolerance note from the MS28775 Revision E sheet (1984-03-23) and its cancellation notice (2000-09-29), DLA ASSIST, read 2026-10-04; the other part numbers' dash-to-size mapping and tolerance note from the MS29513 Revision C sheet (1966-09-16, read 2026-09-27) and MS9386 Revision B sheet (1975-01-17, read 2026-09-27), DLA ASSIST; the other part numbers' statuses from DLA ASSIST document details, idents 33814 (MIL-P-83461/1), 33574 (MIL-R-83248/1), 33575 (MIL-R-83248/2), 33840 (MIL-R-83485/1), 18214 (MIL-DTL-25988/1), 18215 (MIL-DTL-25988/2), 18216 (MIL-DTL-25988/3), 18217 (MIL-DTL-25988/4) and 5334 (MIL-P-5315), read 2026-09-24; SAE Mobilus current-revision records AS83248/2A, read 2026-09-28; AS83461/1C, AS3209C, AS83248/1A, AS3581A, AS29513C, AS3582 and AS9386B, read 2026-09-27; the MIL-R-83248/1A cancellation notice (Notice 5, 2008-07-24), DLA ASSIST, read 2026-09-29; the SAE-AS83248/2 adoption record, DLA ASSIST ident 286631, read 2026-09-28; the polymers from the Parker® O-Ring Handbook ORD 5700A/US, section 8, pages 8-2, 8-4 and 8-5 (read 2026-09-24); the back-up ring pairing and cut styles from the same handbook, section 6, pages 6-8 and 6-9 (read 2026-09-25); SAE AS8791 and the drawings' status from the MS28774M and MS27595E drawings, DLA ASSIST (read 2026-09-28). Facts are stated in our own words and arrangement; no standard's text or table is reproduced.
Parker is a trademark of Parker Hannifin Corporation; no affiliation or endorsement is implied.
Setting Conquest Seal up as a supplier?
Orders are handled under Conquest Seal's AS9100D quality management system, whose certificate scope includes distribution.
Need MS28775-021 with certification?
Send the part number as the print reads it, the quantity and the paperwork the order needs. A Conquest representative replies within one business day. A person answers (714) 632-9830, Pacific business hours.
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