- Family
- NBR (nitrile)
- Standard range
- -34 C to 100 C (Parker® O-Ring Handbook ORD 5700)
- Special grades
- to -57 C, to 121 C
- Durometers
- 40 to 90 Shore A across the nitrile compounds Parker's handbook catalogues (Table 8-5); 70 A is its stock grade (N0674-70 kit, page 3-6)
- Standards
- ASTM D1418 NBR; MIL-PRF-25732, AMS-P-83461, AMS-P-5510
- Product
- O-rings in AS568 and ISO 3601 sizes, quoted in the compound the print names
Service temperatures here are the family figures published in Parker O-Ring Handbook ORD 5700A/US §2.2; the compound datasheet and your application govern the final choice.
Larger and non-standard sizes: an O-ring beyond the molded size lists can be supplied as a spliced and vulcanized O-ring, which the maker joins from cord of the same compound. That page lists, family by family, which makers offer the compound as cord, and what to send for a quote.
Buna-N O-rings are the nitrile (NBR) seal under its original trade name: the economical, tough, oil-resistant ring that most industrial equipment was designed around, rated by the Parker O-Ring Handbook (ORD 5700) from -34 C (-29 F) to 100 C (212 F) with low-temperature compounds to -57 C and short-term service to 121 C. Buyers who learned the material as Buna-N find the same part here: Conquest supplies Buna-N O-rings in every AS568 and metric size, and we stock every AS568 size.
What "Buna-N" tells you on a print
The name dates from the original German trade name for butadiene rubbers; the N marks the acrylonitrile copolymer that gives the material its oil resistance. On a drawing it means nitrile of unstated grade, so the durometer and the compound sheet carry the real specification. Older prints add a hardness ("Buna-N 70"), a maker's compound code (for example N0674-70: N for nitrile, 0674 the compound, 70 the hardness), or a military document for hydraulic and fuel service.
Buna-N O-ring specifications
| Property | Value | Source |
|---|---|---|
| Continuous service temperature | -34 C to 100 C (-29 F to 212 F); low-temperature compounds to -57 C; short term to 121 C | Parker ORD 5700 |
| Material designation | NBR under ASTM D1418 | ASTM naming |
| Common callouts | MIL-PRF-25732 (MS28775), AMS-P-83461 (M83461/1), AMS-P-5510 (MS28778), MIL-P-5315 (MS29512, MS29513) | DLA ASSIST record, read 2026-09-24; AMS-P-5510 per the Parker handbook's section 8 tables, read 2026-09-24 |
| Compliance available | FDA-compliant nitrile compounds (for example Parker N1220-70) on request; 21 CFR 177.2600 is the FDA regulation for rubber articles intended for repeated use | Parker O-Ring Division compound report KK2215 (N1220-70); 21 CFR 177.2600 (eCFR) |
| Related material | HNBR: the same oil resistance plus ozone and heat to 149 C | Parker ORD 5700 |
| Strong against | Petroleum oils and greases, hydraulic fluids, water, dilute acids and alkalis, silicone greases; good abrasion resistance | Parker ORD 5700 section 2.2 |
| Weak against | Ozone, sunlight and weathering, ketones, chlorinated and aromatic hydrocarbons, glycol brake fluid | Parker ORD 5700 section 2.2 |
| Dynamic service | Suitable; the standard hydraulic rod and piston seal material | Parker ORD 5700 |
Sizes and forms we supply
Every AS568 size, the general-purpose dash sizes and the boss-seal sizes alike, and the ISO 3601 metric series, in the durometers listed above; O-ring cord for rings spliced and vulcanized by the maker in odd diameters (static service only); and X-rings and backup rings in the same families. The AS568 chart and the metric chart carry the dimensions, and the dash number guide explains the numbering.
Where Buna-N works, and where it fails
| Media or condition | NBR verdict | Why, per the Parker O-Ring Handbook | Use instead |
|---|---|---|---|
| Hydraulic oil (mineral), engine oil, grease | Excellent | The core nitrile application | FKM above 100 C |
| Gasoline and diesel | Good | High-acrylonitrile grades resist fuel; aromatics and modern blends swell it more | FKM for aromatic-rich fuels |
| Water, glycol-water coolant | Good | Handles water at moderate temperature | EPDM for hot water and steam |
| Dilute acids and alkalis | Acceptable | Moderate resistance | EPDM rates better in dilute acids and alkalis |
| Ozone, sunlight, outdoor service | Not recommended | Plain nitrile cracks in ozone; the handbook flags it | EPDM, HNBR or FKM |
| Ketones, chlorinated solvents, aromatics | Not recommended | Swell and attack | EPDM for ketones; FKM for solvents and aromatics |
| Glycol brake fluid | Not recommended | The handbook rule: brake fluid is butyl or EPDM only | EPDM |
| Steam | Not recommended | Above the material's temperature and hydrolysis limits | EPDM |
| Continuous service above 100 C | Out of range | Short excursions to 121 C only | HNBR to 149 C; FKM to 204 C |
Which specifications call out nitrile O-rings?
Hydraulic and fuel-system prints call out nitrile by military and SAE document numbers. Most of the military originals are inactive or cancelled while the part numbers stay in daily use; statuses below are read from the DLA ASSIST and SAE Mobilus records, read 2026-09-24. Temperatures that appear in some document titles are test conditions, not service limits, and are not repeated here.
| Specification | Part numbers | Service named | Status |
|---|---|---|---|
| MIL-PRF-25732 (older prefixes MIL-P-25732, MIL-DTL-25732) | MS28775-XXX, now AS28775 | Petroleum hydraulic fluid (MIL-H-5606) | Inactive (DLA ASSIST, revision E, 2024) |
| SAE AMS-P-25732 | MS28775-XXX | Petroleum hydraulic fluid | Cancelled August 2003 (SAE record) |
| MIL-P-83461 / SAE AMS-P-83461 | M83461/1-XXX | Petroleum hydraulic fluid, improved performance | MIL document cancelled 2003; the SAE document is current |
| MIL-P-5315 / SAE AMS-P-5315 | MS29512, MS29513 | Aircraft fuels | MIL document cancelled; SAE successor |
| SAE AMS-P-5510 (supersedes MIL-P-5510) | MS28778, now AS28778 (revision C, 2016, reaffirmed 2021) | Straight-thread boss fittings, hydraulic oil | 85 to 95 Shore A boss gaskets in the Parker handbook's section 8 table |
The mil-spec chart lists the full set. Parts to these documents are made by manufacturers on the relevant qualified products list, where the document has one; Conquest supplies them with the certification paperwork.
Buna-N against the alternatives
| If the problem with Buna-N is | Families a print may allow | Why |
|---|---|---|
| Ozone cracking outdoors | HNBR or EPDM | Saturated backbones resist ozone |
| Temperature above 100 C continuous | HNBR to 149 C, Viton® to 204 C | Heat ceiling |
| Aromatic or alcohol-blended fuel | Viton | Swell in modern fuels |
| Water, steam, brake fluid | EPDM | Polar media |
| Cold start below -34 C | Low-temperature nitrile (MS28775-type compounds) | Low-acrylonitrile grades stay flexible |
| Abrasion and extrusion at high pressure | Polyurethane | High abrasion and extrusion resistance |
The nitrile O-ring page covers the same material under its generic name, and the Buna-N vs Viton comparison the upgrade decision.
Sources: 21 CFR 177.2600; AMS-P-5510; AMS-P-83461; AS568; ASTM D1418; ISO 3601; MIL-P-5315; MIL-PRF-25732; MS28775; MS28778; MS29512; MS29513; ORD 5700; Parker O-Ring Handbook; Parker O-Ring Handbook ORD 5700, section 2.2 (read 2026-09-14) and section 8 (read 2026-09-24); Parker O-Ring Handbook ORD 5700, hardness guidance (page 2-10), stock O-ring kits (page 3-6) and Table 8-5 compound hardness, read 2026-09-25; DLA ASSIST and SAE Mobilus records for MIL-PRF-25732, MIL-P-83461, AMS-P-83461, MIL-P-5315, AMS-P-5315, AMS-P-25732, AS28775, AS83461/1, AS28778, AS29512 and AS29513, read 2026-09-24, 2026-09-25 and 2026-09-27.
Parker is a trademark of Parker Hannifin Corporation. Viton is a trademark of The Chemours Company. No affiliation with or endorsement by either trademark owner is implied.
Frequently asked
Is Buna-N still made?
Yes; the name is old, the material is a widely used O-ring elastomer in industry. Ask for nitrile or Buna-N and you get the same part.
Can I use a Buna-N O-ring in a brake system?
No. Glycol brake fluid attacks nitrile; EPDM is the usual brake-fluid material.
What is cork-Buna?
Cork granules bound in nitrile: a conformable gasket sheet, not an O-ring material. See the nitrile gasket page.
Are nitrile, NBR and Buna-N the same material?
Yes. NBR is the ASTM designation, nitrile the common name, Buna-N the old trade name. "Nitrile" is what most buyers type, so both names appear on this site.
Can I use a nitrile O-ring outdoors?
Not plain nitrile; ozone and sunlight crack it. Use EPDM where oil is absent, HNBR or FKM where oil is present.
What is the difference between 70 A and 90 A nitrile?
Hardness. 70 A is the general-purpose default; 90 A resists extrusion at high pressure and is the conventional choice for boss gaskets. The durometer guide explains the trade-off.
Is nitrile food grade?
Specific nitrile compounds are offered FDA compliant for oil-contact food machinery; compliance belongs to the compound, not the family. See the FDA and food-grade guide.
What is HNBR?
Hydrogenated nitrile: nitrile's oil resistance with ozone resistance and a higher temperature ceiling. It is the automotive air-conditioning and coolant seal material; the HNBR O-ring page carries its range.
Which nitrile part standards are current?
AS28775 (revision A of 2008, reaffirmed 2025) for the MS28775 hydraulic family, AS83461/1 for the M83461/1 family, AS28778 for the MS28778 boss gaskets, and AS29512 and AS29513 for the MS29512 and MS29513 families; those four are at revision C (2016), reaffirmed 2021. The MS numbers on older drawings are legacy callouts for the same parts.
What temperature range does nitrile cover?
On the Parker handbook, nitrile runs -34 C to 100 C continuous, low-temperature compounds to -57 C and short-term service to 121 C; the compound datasheet governs. The cold end belongs to the compound, so name the coldest start on the request.
How is a nitrile compound called out in D2000?
A D2000 line callout names a type and a class: the first letter is the heat-aging type and the second the oil-swell class. The letter-to-value tables sit inside the standard, so send the callout as printed and the compound is quoted to it.
Orders are handled under Conquest Seal's AS9100D quality management system, whose certificate scope includes distribution.
Send the part number and the quantity for Buna-N
The AS568 dash number or the inside diameter and cross-section, the durometer, the quantity, the medium and temperature, and any specification the print names. A Conquest representative replies. Quotes answered within one business day. A person answers (714) 632-9830, Pacific business hours.
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