Mil-spec part number, M25988/1, /2, /3 and /4 family
M25988/1-215 O-ring: fluorosilicone (FVMQ), the AS568-215 size
M25988/1-215 is the AS568-215 O-ring size, 1.046 in (26.57 mm) inside diameter by 0.139 in (3.53 mm) cross-section, in fluorosilicone (FVMQ) procured to MIL-DTL-25988/1 (the DLA ASSIST title names Class 1, Grade 70). The DLA ASSIST and SAE Mobilus records read: Active (MIL-DTL-25988/1); AMSR25988B current (2023). The dash sets the size and the document sets the compound, so an AS568-215 in another compound is not the same part as M25988/1-215. Send the designator exactly as the print reads and we quote it against that document.
- Inside diameter
- 1.046 in26.57 mm, +/- 0.010 in
- Cross-section
- 0.139 in3.53 mm, +/- 0.004 in
- AS568 size
- AS568-2152xx series
- Document status
- ActiveMIL-DTL-25988/1
Part facts
| Item | Value |
|---|---|
| Part number | M25988/1-215 |
| NSN | 5331-00-279-9404 (DLA FLIS, read 2026-10-08) |
| Stock | In stock in Orange, CA |
| Procured to | MIL-DTL-25988/1 (Class 1, Grade 70 in the DLA ASSIST title) |
| SAE document | SAE AMS-R-25988 |
| Status | Active (MIL-DTL-25988/1); AMSR25988B current (2023) |
| Base polymer | Fluorosilicone (FVMQ) |
| AS568 size | AS568-215 |
| CAD for the AS568-215 size | AS568-215 STEP 3D solid, AS568-215 DXF 2D drawing, AS568-215 PDF dimensioned drawing; generated from the AS568 nominal dimensions, so verify against your drawing |
| Back-up rings | MS28774-215 (single-turn scarf-cut PTFE) or MS27595-215 (continuous PTFE), both procured to SAE AS8791; both drawings are inactive for new design |
| Dimension | Value | Tolerance |
|---|---|---|
| Inside diameter (ID) | 1.046 in 26.57 mm | +/- 0.010 in (0.25 mm) |
| Cross-section (W) | 0.139 in 3.53 mm | +/- 0.004 in (0.10 mm) |
| Outside diameter (reference) | 1.324 in 33.63 mm | derived: ID + 2 x W |
Millimeter values are converted from the inch table. The M25988 slash sheet carries the class and grade; the base document carries the qualification list. The slash sheets are Active; the base MIL-DTL-25988D was noted inactive for new design on 2025-06-11 and in part superseded by SAE AMS-R-25988, which SAE had cancelled in August 2017 (DoD withdrew its adoption on 2018-01-02) and reissued as revision B in June 2023 (DLA ASSIST, read 2026-09-24 and 2026-09-28; SAE Mobilus, read 2026-09-27).
Same nominal size, other documents
Other part numbers for the AS568-215 size
These part numbers name the AS568-215 nominal size under a different document, so each one is a different compound. They are not interchangeable with M25988/1-215 unless the print or the buyer's engineering allows it. At this size the family sheets for MS28775-215, MS29513-215 and AS9386-215 hold a tighter inside-diameter tolerance than AS568.
| Part number | Document | Polymer | Status |
|---|---|---|---|
| MS28775-215 | MIL-PRF-25732 (MS28775 part drawing) | NBR | Inactive (MIL-PRF-25732); AS28775A current |
| M83461/1-215 | MIL-P-83461/1 | NBR | Canceled; AS83461/1C current |
| M83248/1-215 | MIL-R-83248/1 (Class 1) | FKM | Canceled; AS3209C stabilized; AS83248/1A current |
| M83248/2-215 | MIL-R-83248/2 (Class 2) | FKM | Canceled; AS3581A stabilized; AS83248/2A current |
| AS3209-215 | SAE AS3209 (AMS7276) | FKM | AS3209C stabilized |
| M83485/1-215 | MIL-R-83485 | FKM, low-temperature grade | Canceled |
| M25988/2-215 | MIL-DTL-25988/2 | FVMQ | Active |
| M25988/3-215 | MIL-DTL-25988/3 | FVMQ | Active |
| M25988/4-215 | MIL-DTL-25988/4 | FVMQ | Active |
| MS29513-215 | MIL-P-5315 (MS29513 part drawing) | NBR | Canceled (MIL-P-5315); AS29513C current |
| AS3582-215 | SAE AS3582 (AMS3304) | VMQ silicone | AS3582 current |
| AS9386-215 | SAE AS9386 (AMS7267) | VMQ silicone | AS9386B current |
The base polymer
M25988/1-215 is fluorosilicone (FVMQ). The Parker® O-Ring Handbook ORD 5700 range published for the FVMQ family (section 2.2) is -73 C to 177 C. That is the polymer family's range, not this document's requirement; the compound sheet for the qualified grade governs.
Material page: Fluorosilicone (FVMQ) O-rings. Every document in the family: M25988/1, /2, /3 and /4 O-rings.
Nearby M25988/1 part numbers
| Part number | ID in | ID mm | W in | W mm |
|---|---|---|---|---|
| M25988/1-211 | 0.796 | 20.22 | 0.139 | 3.53 |
| M25988/1-212 | 0.859 | 21.82 | 0.139 | 3.53 |
| M25988/1-214 | 0.984 | 24.99 | 0.139 | 3.53 |
| M25988/1-215 | 1.046 | 26.57 | 0.139 | 3.53 |
| M25988/1-220 | 1.359 | 34.52 | 0.139 | 3.53 |
| M25988/1-222 | 1.484 | 37.69 | 0.139 | 3.53 |
| M25988/1-223 | 1.609 | 40.87 | 0.139 | 3.53 |
Frequently asked
What is the AS568 equivalent of M25988/1-215?
M25988/1-215 is the AS568-215 size: 1.046 in (26.57 mm) inside diameter by 0.139 in (3.53 mm) cross-section. The dash sets the size; MIL-DTL-25988/1 sets the fluorosilicone (FVMQ) compound. An AS568-215 ring in any other compound has the same dimensions but is not the same part as M25988/1-215.
What is the NSN for M25988/1-215?
DLA's public FLIS data lists M25988/1-215 on NSN 5331-00-279-9404 (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-DTL-25988/1 still active?
The document status reads: Active (MIL-DTL-25988/1); AMSR25988B current (2023). It comes from the DLA ASSIST and SAE Mobilus records listed under Sources, with the date each was read.
How do I order M25988/1-215?
Send the designator exactly as the print reads, with its revision, any suffix letter, the quantity and the paperwork the order needs. M25988/1-215 is quoted and supplied against MIL-DTL-25988/1 or SAE AMS-R-25988, 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, idents 18213 (MIL-DTL-25988), 18214, 18215, 18216, 18217 (slash sheets /1 to /4), read 2026-09-24; DLA ASSIST Document ID search for MIL-DTL-25988 (five records: the base document and slash sheets /1 to /4), read 2026-09-28; DLA ASSIST: the SAE-AMS-R-25988 withdrawal of adoption notice (2018-01-02, ident 211298) and MIL-DTL-25988D Notice 1 (2025-06-11, inactive for new design, in part superseded by SAE-AMS-R-25988), read 2026-09-28; SAE Mobilus: AMSR25988B (revised June 2023; revision A cancelled August 2017), read 2026-09-27; 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 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 from the Freudenberg Sealing Technologies, Aerospace Part and Material Cross-Reference brochure (July 2024), pages 3 and 4, read 2026-10-13; the other part numbers' dash-to-size mapping and tolerance note from the MS28775 Revision E sheet (1984-03-23, read 2026-10-04), 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 18115 (MIL-PRF-25732), 33814 (MIL-P-83461/1), 33574 (MIL-R-83248/1), 33575 (MIL-R-83248/2), 33840 (MIL-R-83485/1), 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; AS28775A, read 2026-09-25; 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); Parker O-Ring Handbook ORD 5700A/US, section 2.2, for the polymer family range (read 2026-09-14). 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 M25988/1-215 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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