Aerospace O-ring family, ethylene propylene, phosphate-ester fluid
NAS1611 O-rings: ethylene propylene for phosphate-ester hydraulic fluid
NAS1611 is the AIA National Aerospace Standard for a phosphate-ester resistant ethylene propylene (EPDM) O-ring, and NAS1612 is the same kind of packing for straight-thread tube-fitting bosses. Both are Active: NAS1611 at Revision 12 and NAS1612 at Revision 8, each dated 2014-06-30. DoD adopted both in 1995, and DLA ASSIST lists the adoptions as Active, reaffirmed in 2018. Neither record gives them an AS568 size, so we quote the part number exactly as your print reads it. One manufacturer's 2024 cross-reference builds both in compounds made to NAS1613, the AIA ethylene propylene material specification, now at Revision 6.
- Polymer
- Ethylene propylene (EPDM)phosphate-ester resistant
- Current revisions
- Rev 12 and Rev 8NAS1611 and NAS1612, AIA, 2014
- DoD adoption
- Activeadopted 1995, reaffirmed 2018
- QPL
- None on recordAIA keeps none for NAS parts
Specification: documents, status, material
| Item | Value | Source |
|---|---|---|
| Standard-size part standard | NAS1611, packing, ethylene propylene, preformed O-ring, phosphate-ester resistant: Active at Revision 12 (2014-06-30); DoD-adopted 1995-09-29, reaffirmed 2018-09-01, Active | AIA standards store and DLA ASSIST, read 2026-09-27 |
| Boss-size part standard | NAS1612, ethylene propylene preformed O-ring packing for straight-thread tube-fitting bosses, phosphate-ester resistant: Active at Revision 8 (2014-06-30); DoD-adopted 1995-09-29, reaffirmed 2018-09-01, Active | AIA standards store and DLA ASSIST, read 2026-09-27 |
| Material specification | NAS1613, packing, preformed, ethylene propylene rubber, for elastomer seal elements in hydraulic systems on phosphate-ester fluids: Active at Revision 6 (2012-11-30); DoD-adopted 1995-09-29, reaffirmed 2018-09-01, Active | AIA standards store and DLA ASSIST, read 2026-09-27 |
| Material behind NAS1611 and NAS1612 | Not named in the AIA or DLA records; one manufacturer's 2024 cross-reference builds both part numbers in its NAS1613 compounds | AIA and DLA ASSIST records; one manufacturer's cross-reference (2024), read 2026-09-27 |
| Size | No AS568 equivalence is on record: the AIA and DLA records give no dash-to-AS568 correspondence, and one manufacturer's 2024 cross-reference lists the parts as inquire, with parts over 0.500 in inside diameter held tighter than standard AS568 tolerance; the drawing sets the size | AIA and DLA ASSIST records; one manufacturer's cross-reference (2024), read 2026-09-27 |
| The -A suffix | The AIA and DLA records do not define the suffix; Freudenberg's 2024 aerospace cross-reference builds NAS1611-XXXA and NAS1612-YYA parts in its NAS1613 Revision 6 compound and the unsuffixed parts in its Revision 2 compound. Send the suffix exactly as printed | Freudenberg Sealing Technologies, Aerospace Part and Material Cross-Reference (brochure, July 2024), https://www.fst.com/-/media/files/brochures/en/fst-aerospace-parts-cross-reference-brochure.pdf, page 3 |
| Base polymer | Ethylene propylene (EPDM) | document titles |
| Durometer | Manufacturers supply this family at 80 (Parker® ORD 5700 (2021) Table 8-4 lists its NAS1613 Revision 5 compound in the 75 to 85 band); confirm the durometer against your print | Parker ORD 5700 (2021); one manufacturer's cross-reference (2024) |
| QPL | None on record: AIA keeps no qualified products list for NAS parts, and the DLA ASSIST records carry none; the part manufacturer gives the purchaser its qualification report and certificate of conformance | AIA standards FAQ and DLA ASSIST, read 2026-09-27 |
| Service | Phosphate-ester hydraulic fluid: the NAS1611 and NAS1612 titles read phosphate-ester resistant, and NAS1613 covers seal elements for hydraulic systems on phosphate-ester fluids | AIA and DLA ASSIST document titles |
| Compounds manufacturers pair with NAS1613 | Parker ORD 5700 (2021) Table 8-4 pairs E0515 with NAS1613 Revision 2 and E1267-80 with Revision 5; no Parker pairing with the current Revision 6 is on record | Parker ORD 5700 (2021) |
Status strings are quoted as DLA ASSIST and SAE Mobilus print them (Canceled is ASSIST's spelling; Inactive means inactive for new design; Withdrawn is SAE's word). Conquest Seal is a distributor and is not itself listed on any qualified products list.
Where the documents stand
NAS1611, NAS1612 and NAS1613 are National Aerospace Standards, published and sold by the Aerospace Industries Association (AIA), which is why they behave differently from every MIL and SAE family on this site. The AIA store lists all three as Active: NAS1611 at Revision 12 and NAS1612 at Revision 8, both dated 2014-06-30, and NAS1613 at Revision 6, dated 2012-11-30. DoD adopted all three on 1995-09-29, and DLA ASSIST shows each adoption Active, reaffirmed on 2018-09-01. DLA holds only the one-page adoption notices; the standards themselves are bought from AIA.
Neither the AIA nor the DLA records give NAS1611 or NAS1612 an AS568 size, name NAS1613 as their material or define the -A suffix. Those points come from Freudenberg Sealing Technologies' Aerospace Part and Material Cross-Reference (brochure, July 2024, page 3), which builds the -A parts in its NAS1613 Revision 6 compound and the unsuffixed parts in its Revision 2 compound, and lists the sizes as inquire, with parts over 0.500 in inside diameter held tighter than AS568. The drawing governs, so send the part number exactly as printed, suffix included, and we quote to it.
The base polymer
The polymer behind this family is ethylene propylene (EPDM). The Parker O-Ring Handbook ORD 5700 family range for EPDM (section 2.2, read 2026-09-14) is -57 C to 150 C; that is the polymer family's range, not this document's requirement, and the compound sheet for the qualified grade governs. Parker notes that specification temperature limits do not necessarily represent operating temperature limits.
Material page: Ethylene propylene (EPDM) O-rings. Temperature ranges by family: O-ring temperature ranges.
How we quote this family
Send the part number exactly as printed, including any -A suffix, for example NAS1611-XXX or NAS1611-XXXA, with the quantity and the certification the order needs. We quote it supplied against NAS1611 or NAS1612, in the ethylene propylene compound your print calls for, with a certificate of conformance and lot traceability. If your print names the NAS1613 revision or a compound, include it. The part number goes on the quote as you send it, and no AS568 size is substituted for it.
Related pages
Other families: MS28775, M83461/1, M83248/1 and M83248/2, M83485/1, M25988/1, /2, /3 and /4, MS29513 and MS29512, AS3582, AS9386 and AS9385, AS3209 and AS3208.
Frequently asked
What does NAS1611 specify?
NAS1611 is the AIA National Aerospace Standard for a phosphate-ester resistant ethylene propylene O-ring, Active at Revision 12 (2014-06-30). NAS1612 covers the same kind of packing for straight-thread tube-fitting bosses, Active at Revision 8 (2014-06-30). NAS1613 is the AIA ethylene propylene material specification for seal elements in phosphate-ester hydraulic systems, Active at Revision 6 (2012-11-30). DoD adopted all three in 1995, and DLA ASSIST lists each adoption as Active, reaffirmed in 2018.
Is a NAS1611 O-ring the same size as the AS568 dash?
Neither the AIA nor the DLA record gives NAS1611 or NAS1612 an AS568 size, and neither defines the -A suffix. One manufacturer's 2024 cross-reference lists the parts as inquire, with parts over 0.500 in inside diameter held tighter than AS568, so the drawing sets the size. Send the part number as printed, suffix included, and we quote that part number.
What does the A suffix on a NAS1611 part mean?
Neither the AIA nor the DLA record defines it. One manufacturer's 2024 cross-reference builds the -A part in its NAS1613 Revision 6 compound and the unsuffixed part in its Revision 2 compound. Treat that as one maker's usage, and send the suffix exactly as the print shows it.
What O-ring should I use for phosphate-ester hydraulic fluid?
Ethylene propylene. The NAS1611 and NAS1612 titles read phosphate-ester resistant ethylene propylene, and NAS1613 covers ethylene propylene seal elements for hydraulic systems on phosphate-ester fluids. Ethylene propylene is chosen for these fluids where nitrile and fluorocarbon are not. The choice belongs to your print or your system specification; send the callout it names and we quote that part.
Is there a QPL for NAS1611 or NAS1613?
No. AIA, which publishes the NAS documents, keeps no qualified products list for NAS parts, and the DLA ASSIST records carry none. AIA leaves the check to the purchaser: review the standard and the part manufacturer's qualification report. We supply the part with the manufacturer's certificate of conformance and lot traceability.
Related guides
Sources
AIA standards store records for NAS1611 (Revision 12), NAS1612 (Revision 8) and NAS1613 (Revision 6), read 2026-09-27; DLA ASSIST document details for NAS1611, NAS1612 and NAS1613 (adopted 1995-09-29, reaffirmed 2018-09-01), read 2026-09-27; Aerospace Industries Association, Purchase Standards page and its QPL answer (aia-aerospace.org/standards), read 2026-09-27; Parker O-Ring Handbook ORD 5700 (2021), Table 8-4, for the compound pairings; Freudenberg Sealing Technologies, Aerospace Part and Material Cross-Reference (brochure, July 2024), read 2026-09-27, for the -A suffix usage, the NAS1613 pairing and the tolerance note. 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. Compound pairings are the named manufacturer's published statements, not qualified products list entries.
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 NAS1611 and NAS1612 with certification?
Send the designator as the print reads it, the dash, the quantity and the paperwork the order needs. A Conquest representative replies with the part quoted against the document. Quotes answered within one business day. A person answers (714) 632-9830, Pacific business hours.
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