What is NBR (Nitrile)?

  • Phil Hayton
  • Reviewed August 2026
  • 4 min read

Quick answer

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At a glance

Best for
mineral oils, fuels, hydraulics
Avoid with
ozone, steam, break fluid
Temperature
-30 to +100°C
Also known as
Buna-N, nitrile

The full explanation

The full explanation

NBR is a synthetic rubber made by combining acrylonitrile and butadiene. The more acrylonitrile in the mix, the better the oil resistance but the stiffer the rubber gets in the cold. Standard grades strike the balance that suits most workshop and automotive jobs.

It seals well against mineral oils, petrol, diesel, greases and hydraulic fluids, and it costs less than any comparable material. That combination is why roughly 8 in 10 O-rings sold are NBR.

Hardness matters too. Shore 70 is the standard for general use. Shore 90 is firmer and resists extrusion in high-pressure joints. If you're unsure, our Shore hardness guide explains the difference.

Common mistakes

  • Using NBR outdoors. Sunlight and ozone crack it. Use EPDM for outdoor jobs.
  • Using NBR with steam or hot water. It hardens and fails. EPDM is the right choice.
  • Using NBR with break fluid. Glycol-based fluids attack it. Use EPDM for brake systems.

Frequently asked questions

Is NBR the same as Buna-N?
{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Yes. Buna-N and nitrile are both trade names for the same NBR rubber."}]}]}
Is NBR food safe?
{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Standard NBR is not food safe. For food and drink equipment use FDA-grade silicone or EPDM instead."}]}]}
Is NBR fuel resistant?
{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Yes. NBR handles petrol and diesel well up to around 100°C. For hotter fuel systems, step up to FKM."}]}]}

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