Mil-spec part number, M25988/1, /2, /3 and /4 family

M25988/1-203 O-ring: fluorosilicone (FVMQ), the AS568-203 size

M25988/1-203 is the AS568-203 O-ring size, 0.296 in (7.52 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 AS568-203 in another compound is not the same part as M25988/1-203. Send the designator exactly as the print reads and we quote it against that document.

Inside diameter
0.296 in7.52 mm, +/- 0.005 in
Cross-section
0.139 in3.53 mm, +/- 0.004 in
AS568 size
AS568-2032xx series
Document status
ActiveMIL-DTL-25988/1
Request a quote for M25988/1-203 M25988/1, /2, /3 and /4 family AS568-203 size page
OD 0.574 in (14.58 mm) ref ID 0.296 in (7.52 mm) W 0.139 in (3.53 mm) section A-A M25988/1-203 AS568, inch authoritative
Dimensioned from the AS568 table for AS568-203, the size M25988/1-203 names. Not to scale.

Part facts

M25988/1-203: document, status, polymer and size
ItemValue
Part numberM25988/1-203
StockIn stock in Orange, CA
Procured toMIL-DTL-25988/1 (Class 1, Grade 70 in the DLA ASSIST title)
SAE documentSAE AMS-R-25988
StatusActive (MIL-DTL-25988/1); AMSR25988B current (2023)
Base polymerFluorosilicone (FVMQ)
AS568 sizeAS568-203
CAD for the AS568-203 sizeAS568-203 STEP 3D solid, AS568-203 DXF 2D drawing, AS568-203 PDF dimensioned drawing; generated from the AS568 nominal dimensions, so verify against your drawing
Back-up ringsMS28774-203 (single-turn scarf-cut PTFE) or MS27595-203 (continuous PTFE), both procured to SAE AS8791; both drawings are inactive for new design
M25988/1-203: dimensions and tolerances from the AS568 table
DimensionValueTolerance
Inside diameter (ID)0.296 in 7.52 mm+/- 0.005 in (0.13 mm)
Cross-section (W)0.139 in 3.53 mm+/- 0.004 in (0.10 mm)
Outside diameter (reference)0.574 in 14.58 mmderived: 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 The slash sheets are Active; the base MIL-DTL-25988D was noted inactive for new design on 2025-06-11 and in part superseded by SAE AMS-R-25988, which SAE had cancelled in August 2017 (DoD withdrew its adoption on 2018-01-02) and reissued as revision B in June 2023 (DLA ASSIST, read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 AS568-203 size

These part numbers name the AS568-203 nominal size under a different document, so each one is a different compound. They are not interchangeable with M25988/1-203 unless the print or the buyer's engineering allows it.

Part standards that call out the AS568-203 nominal size
Part numberDocumentPolymerStatus
MS28775-203MIL-PRF-25732 (MS28775 part drawing)NBRInactive (MIL-PRF-25732); AS28775A current
M83461/1-203MIL-P-83461/1NBRCanceled; AS83461/1C current
M83248/1-203MIL-R-83248/1 (Class 1)FKMCanceled; AS3209C stabilized; AS83248/1A current
M83248/2-203MIL-R-83248/2 (Class 2)FKMCanceled; AS3581A stabilized; AS83248/2A current
AS3209-203SAE AS3209 (AMS7276)FKMAS3209C stabilized
M83485/1-203MIL-R-83485FKM, low-temperature gradeCanceled
M25988/2-203MIL-DTL-25988/2FVMQActive
M25988/3-203MIL-DTL-25988/3FVMQActive
M25988/4-203MIL-DTL-25988/4FVMQActive
AS3582-203SAE AS3582 (AMS3304)VMQ siliconeAS3582 current
AS9386-203SAE AS9386 (AMS7267)VMQ siliconeAS9386B current

The base polymer

M25988/1-203 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 numberID inID mmW inW mm
M25988/1-1392.17555.250.1032.62
M25988/1-1402.23756.820.1032.62
M25988/1-1512.98775.870.1032.62
M25988/1-2030.2967.520.1393.53
M25988/1-2100.73418.640.1393.53
M25988/1-2110.79620.220.1393.53
M25988/1-2120.85921.820.1393.53
← M25988/1-151M25988/1, /2, /3 and /4 familyM25988/1-210 →

Frequently asked

What is the AS568 equivalent of M25988/1-203?

M25988/1-203 is the AS568-203 size: 0.296 in (7.52 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 AS568-203 ring in any other compound has the same dimensions but is not the same part as M25988/1-203.

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 M25988/1-203?

Send the designator exactly as the print reads, with its revision, any suffix letter, the quantity and the paperwork the order needs. M25988/1-203 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; 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 from the MS28775 Revision E sheet (1984-03-23, read 2026-10-04) 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) and 18217 (MIL-DTL-25988/4), read 2026-09-24; SAE Mobilus current-revision records AS83248/2A, read 2026-09-28; AS83461/1C, AS3209C, AS83248/1A, AS3581A, 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.

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Compliance documents for supplier onboardingQuality and certificationsSecond source for O-rings and sealsStocking and vendor-managed inventorySupplier requirementsVendor consolidation for O-rings, seals and gaskets

Orders are handled under Conquest Seal's AS9100D quality management system, whose certificate scope includes distribution.

Need M25988/1-203 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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