O-rings, military and aerospace specifications
Mil-spec O-rings by designator: MS28775, M83248, M25988 and the AS families
A mil-spec O-ring callout such as M83248/1-214 names a specification family (M83248), a slash sheet or class (/1) and an AS568 dash number for the size (-214); you send it to us exactly as the print reads and we quote it supplied against that document, in the compound the document calls for, made by manufacturers on the relevant qualified products list, where the document has one, with a certificate of conformance. Most of the MIL documents behind these callouts are cancelled or inactive for new design and have SAE successors, so the index below names the current document for each family, the polymer and durometer class, whether a qualified products list exists, and the page that decodes the family.
Every family on this page shares one size system: the three-digit dash is the AS568 dash, so MS28775-214, M83461/1-214 and M83248/1-214 are one size in three materials. Each family page carries a designator-to-AS568 table with the inside diameter and cross-section for ten common dashes, and every dash links to its own size page. The material behind a callout lives in a separate document (MIL-PRF-25732, AMS7276, NAS1613), and that document decides the polymer and the hardness class. Conquest Seal is AS9100 certified.
The families, their current documents and their pages
| Designator family | Current document | Superseded document(s) | Polymer and durometer | QPL | Family page |
|---|---|---|---|---|---|
| MS28775 | SAE-AS28775A (2025-02-08) for the drawing; MIL-PRF-25732 rev E (2024) inactive for new design; SAE-AMS-P-25732A | MIL-P-25732 and MIL-DTL-25732 are the same document (prefix changes); MS drawing status: ask with the quote | Nitrile (NBR); 70 to 80, the Parker® compound's band | Yes: QPL-25732, government (DLA QPD) | Family page |
| M83461/1 | SAE-AS83461/1C (2021-11-08); material SAE-AMS-P-83461 (1998) | MIL-P-83461 and MIL-P-83461/1, cancelled 2003-10-01 | Nitrile (NBR); 75 as supplied | None on record | Family page |
| M83248/1 and M83248/2 | SAE-AS83248/1A on AMS7276 (Class 1); SAE-AS3581A on AMS7259 (Class 2) | MIL-R-83248 (cancelled 2001), /1 (2008), /2 | Fluorocarbon (FKM); 75 (/1), 90 (/2) | SAE non-government QPL on AMS7276 and AMS7259 | Family page |
| M83485/1 | SAE-AMS-R-83485A (2014); manufacturers now cite SAE-AMS7287A (2022) | MIL-R-83485, cancelled 2002-10-23 | Fluorocarbon (FKM), low-temperature grade; 75 as supplied | None on record | Family page |
| M25988/1, /2, /3 and /4 | MIL-DTL-25988/1 to /4, Active (2026-04-21); base MIL-DTL-25988 rev D inactive for new design; SAE-AMS-R-25988B | MIL-R-25988 is the same document (prefix change) | Fluorosilicone (FVMQ); 70 (/1), Class 3 (/2), 60 (/3), 80 (/4) | Yes: QPL-25988, government (DLA QPD) | Family page |
| MS29513 and MS29512 | SAE-AS29513C and SAE-AS29512C (2021-11-09); material SAE-AMS-P-5315C | MIL-P-5315, cancelled 2002-02-28 | Nitrile (NBR); 70 as supplied | None on record | Family page |
| NAS1611 and NAS1612 | NAS1611, NAS1612 and the material NAS1613 (AIA documents): status, ask with the quote | none on record | Ethylene propylene (EPDM); 80 as supplied | No DLA QPL (AIA document) | Family page |
| AS3582 | SAE-AS3582 (2018-08-23) on SAE-AMS3304J (2019) | MS9068 (legacy callout): status, ask with the quote | Silicone (VMQ); 65 to 75 class | Not stated | Family page |
| AS9386 and AS9385 | SAE-AS9386B (2021) and SAE-AS9385A (2020) on SAE-AMS7267H (2021) | MS9386 and MS9385 (legacy callouts): status, ask with the quote | Silicone (VMQ); 70 to 80 class | Not stated | Family page |
| AS3209 and AS3208 | SAE-AS3209C (2021) and SAE-AS3208A (2020) on SAE-AMS7276 (Active) | none (SAE size sheets) | Fluorocarbon (FKM); 70 to 80 class | SAE non-government QPL on AMS7276 | Family page |
The mil-spec chart carries the verified specification register; the O-rings hub lists every compound family we quote. Backup rings (MS28774, MS28782, MS27595 to AS8791) and X-rings have their own pages: backup rings, X-rings.
| Callout | Size sheet | Material document | Polymer and hardness class | QPL |
|---|---|---|---|---|
| AS3581-XXX | SAE-AS3581A (2020-05-12) | SAE-AMS7259, Active | FKM, 85 to 95 | SAE non-government QPL available |
| AS3085-XXX and AS3084-YY (boss) | SAE-AS3085A and SAE-AS3084A (2012-06-06) | SAE-AMS7280F | FKM, 70 to 80 | not stated |
| AS3569-XXX | SAE-AS3569A (2021-08-09) | SAE-AMS7270M | NBR, 65 to 75 | not stated |
| AS3570-XXX | SAE-AS3570A (2025-07-17) | SAE-AMS7274K | NBR, 65 to 75 | not stated |
| AS3551-XXX | SAE-AS3551A (2020-10-09) | SAE-AMS7272G | NBR, 65 to 75 | not stated |
| AS3578-XXX | SAE-AS3578 (2018-08-23) | SAE-AMS7271K | NBR, 60 to 70 | not stated |
| AS28778-YY and MS28778-YY (boss gasket) | SAE-AS28778C (2021-11-08) | AMS-P-5510 (status: ask with the quote) | NBR; 90 by industry convention, not stated in the document | not stated |
| AMS7257-XXX | no separate size sheet | SAE-AMS7257E (2014-09-05) | FFKM, 70 to 80 | not stated |
| MS28774, MS28782, MS27595 (backup rings) | see the backup ring page | SAE-AS8791D (2025-07-16) | PTFE | not stated |
How to read a mil-spec O-ring callout
The family and the dash
Read a callout from left to right: the letters and digits before the dash name the specification family and, where present, its slash sheet; the digits after the dash are the AS568 size. M83248/1-214 is the M83248 family, slash sheet 1 (Class 1, 75 hardness), in the -214 size, which AS568 lists at 0.984 in inside diameter and 0.139 in cross-section. The dash is a catalog lookup and says nothing about the material. MS28775-214, M83461/1-214 and AS3209-214 are the same size in three different documents.
Slash sheets and classes
A slash sheet is a numbered supplement to the base document, and families use it differently. On M83248 the slash sheet is the hardness class: /1 is Class 1 at 75 and /2 is Class 2 at 90. On M25988 the four slash sheets are class and grade combinations of one fluorosilicone: /1 is Class 1 Grade 70, /2 is Class 3, /3 is Grade 60 and /4 is Class 1 Grade 80, as the DLA ASSIST titles print them. On M83461 the slash sheet is the size sheet: /1 covers the standard sizes and /2 the boss sizes.
Suffix letters
A trailing letter on a document number is a revision: AS28775A, AS29513C, AMS7276J. A trailing letter inside a part number can mean something else, so never read it as a revision. On NAS1611 and NAS1612 the -A suffix, as manufacturers use it, marks a compound qualified to NAS1613 Revision 6 while the unsuffixed part is the Revision 2 compound; NAS1613 itself governs. In our own shop records a trailing letter on a part number identifies a compound, not a revision.
Boss sizes, the 9xx dashes
The 900 series of AS568 (dash numbers 901 through 932) covers the straight-thread tube-fitting boss seals, and their cross-section changes with the dash. Several families carry a separate boss designator with a two-digit dash: M83461/2-YY, AS3208-YY, AS3084-YY, AS9385-YY, MS29512-YY and NAS1612-YY each map to AS568-9YY, per the manufacturers' cross-references. The standard-size designator in the same family carries the three-digit dash. If the print shows a two-digit dash on one of these families, it is a boss seal.
The SAE split: an AS number for the size, an AMS number for the compound
The old MIL system bundled the size sheet and the compound into one slash-sheet number, which is why M83248/1 became a pair when it was cancelled: SAE-AS83248/1 for the sizes and SAE-AMS7276 for the compound. In the SAE system the AS document carries the sizes and its title names the AMS material document outright, so AS3209 is the size sheet and AMS7276 is the compound. A complete SAE callout therefore needs both numbers. When a print shows only the AS number, we quote the AMS material its title names.
One dash, every family: the cross-reference concept
M83485/1, AS3582 and AS9386 follow the same pattern: the designator plus the three-digit AS568 dash. 2-XXX dash numbers correspond with AS568, so a Parker 2-214 is the -214 size; the material is a separate question answered by the compound number on the print.
What to send for a quote
Send the designator exactly as the print reads, including the slash sheet and any suffix letter, and the dash number. Add the quantity and the certification the order needs: a certificate of conformance to the document, lot traceability, and any first-article or test-report requirement your quality system imposes. If the print names a compound or a manufacturer, include it; if it names a revision, include that too. We reply with the part quoted in the compound the print names, supplied against the document, and we say so on the paperwork.
- Designator and dash as printed, for example M83248/1-214 or MS28775-214
- Slash sheet, class or grade where the family has one (M25988/3, M83461/2)
- Suffix letter where the print carries one (NAS1611-214A)
- Quantity, and whether it is a one-time buy or a repeating requirement
- Certification: certificate of conformance, lot traceability, cure date, test reports, first article
- The compound or manufacturer if the print or your approved source list names one
What a qualified products list is
A qualified products list names the manufacturers whose product has been tested and listed by the qualifying activity against a governing specification; a distributor is not on it, and Conquest Seal is not on any QPL. The government lists live in DLA's Qualified Products Database, searched by governing specification, and some SAE AMS documents carry a non-government QPL held by SAE.
Of the families on this page, MIL-PRF-25732 (MS28775) and MIL-DTL-25988 (M25988) carry government QPLs, QPL-25732 and QPL-25988. AMS7276 and AMS7259, the compounds behind M83248/1, M83248/2, AS3209 and AS3581, carry SAE non-government QPLs. The cancelled MIL documents (MIL-R-83248, MIL-P-83461, MIL-P-5315, MIL-R-83485) show no QPL on record, and NAS documents are published by the Aerospace Industries Association, not DLA. When a QPL exists we supply parts made by QPL-listed manufacturers and the manufacturer's listing appears on the certification.
Frequently asked
How do I read a mil-spec O-ring callout like M83248/1-214 on a drawing?
M83248 is the specification family, /1 is the slash sheet (Class 1, 75 hardness fluorocarbon) and -214 is the AS568 size: 0.984 in inside diameter, 0.139 in cross-section. The governing MIL document was cancelled in 2008 and its successor is SAE-AS83248/1, an O-ring molded from AMS7276 material, so the same part is quoted against AS83248/1 with AMS7276 as the compound. Read the family, then the slash sheet, then the dash. The M83248 family page walks through both classes.
How do I cross-reference a Parker 2-214 O-ring to a mil-spec part number?
The 2-214 is a size, not a material: Parker's dash numbers correspond with AS568, so 2-214 is the AS568-214 size. The mil-spec designator depends on the compound the print calls for, for example MS28775-214 for the petroleum hydraulic nitrile, M83248/1-214 for the 75 hardness fluorocarbon, or M25988/1-214 for the Class 1 Grade 70 fluorosilicone. Send us the Parker compound number printed beside the size and we match it to the document.
What is the AS568 equivalent of MS28775-214?
The -214 dash is already an AS568 dash: MS28775-214 is the AS568-214 size, 0.984 in inside diameter by 0.139 in cross-section, in the nitrile compound that MIL-PRF-25732 calls for. AS568 fixes the dimensions and MIL-PRF-25732 fixes the material. The SAE successor to the MS drawing is SAE-AS28775, whose title reads Packing, Preformed, MS28775 O-ring.
Which mil-spec O-rings have a QPL, and what does QPL-listed mean?
QPL-listed means a manufacturer's product has been tested and listed by the qualifying activity against the governing specification. On this page the government lists are QPL-25732 (MIL-PRF-25732, the MS28775 family) and QPL-25988 (MIL-DTL-25988, the M25988 family), both in DLA's Qualified Products Database. AMS7276 and AMS7259 carry SAE non-government QPLs. A distributor is never on a QPL; we supply parts made by the listed manufacturers and the listing shows on the certification.
Do I need a certificate of conformance with mil-spec O-rings?
You get one either way: a certificate of conformance ships with every order. It states that the part was supplied against the named document and carries the lot identification that ties it back to the manufacturer. Tell us on the request for quote what else the order needs, because those are the items a purchase order or a customer flow-down has to ask for: cure date, test reports or a first-article inspection report. We quote the certification with the part.
Is a cancelled MIL specification still a valid callout?
Yes. Cancellation is a standardization-office act and the part numbers stay on live drawings; buyers keep ordering MS28775 and M83248/1 by those numbers. The right answer is which document is current: the cancelled MIL document usually names its SAE successor in its own title, and the family pages here name it for you. Inactive for new design means the document is still maintained and still procurable but not for new designs; MIL-PRF-25732 and MIL-DTL-25988 are in that state; 25732 was revised in 2024 and 25988 carries a 2025 inactivation notice on its 2021 revision D.
Where can a small manufacturer buy mil-spec O-rings by part number with traceability?
From a distributor that quotes the designator as printed and supplies the part with the certification the document and your quality system need. Send us the callout, the quantity and the paperwork requirement; we quote the part in the compound the document calls for, made by the manufacturers listed for it where a qualified products list exists, with a certificate of conformance and lot traceability. Standard AS568 sizes cover every family on this page, and each dash has its own size page here.
Related guides
Sources
DLA ASSIST-QuickSearch document details (quicksearch.dla.mil), statuses and supersession read 2026-09-06 and 2026-09-13; SAE Mobilus public standard pages (saemobilus.sae.org), revision letters and dates read 2026-09-06; DLA Qualified Products Database (qpldocs.dla.mil) for the QPL model; QPL-25732-18 Amendment 3 (2006) for the 25732 list's existence; Parker O-Ring Handbook ORD 5700 (2021), Tables 8-3 and 8-4, for compound pairings and the dash correspondence; Section 4.5 for the boss series; Freudenberg Sealing Technologies aerospace part and material cross-reference brochure (2024), for the designation pattern and the standard-versus-boss dash split only; AS568 dimensions from this site's size chart (SAE-AS568F, 2026-01-29). Statuses appear only where a publisher's own page was read; for any other document, ask with the quote. Facts are stated in our own words and our own arrangement; no standard's text or table and no manufacturer's cross-reference table is reproduced.
Parker is a trademark of Parker Hannifin Corporation. No affiliation or endorsement is implied.
Freudenberg is a trademark of its owner; no affiliation or endorsement is implied.
Send the callout as the print reads it
Designator, slash sheet, dash, quantity and the certification the order needs. A Conquest representative replies with the part quoted against the document.
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