---
title: "NBR (Nitrile) Metric O-Rings (ISO 3601)"
description: "NBR (Nitrile) Metric O-Rings (ISO 3601) (acrylonitrile-butadiene rubber, typically 70 Shore A): good resistance to mineral oil, grease and hydraulic fluid;"
url: https://engineeringhardware.com/guide/material/nbr-metric-o-rings/
source: Engineering Hardware & Fasteners
---

# NBR (Nitrile) Metric O-Rings (ISO 3601)

Seals · ISO 3601-1 (fluid power — O-rings, inside diameters and cross-sections)

Temperature range, chemical and fluid compatibility, hardness and the full dimensional range for this compound.

NBR (Nitrile) Metric O-Rings (ISO 3601) are supplied to acrylonitrile-butadiene rubber, typically 70 Shore A. Corrosion behaviour is good resistance to mineral oil, grease and hydraulic fluid; poor in ozone and weathering, the material is non-magnetic, and the usable service range is approx. -30 °C to +100 °C. In practice this grade is the default elastomer for oil and hydraulic sealing.

- **Grade:** acrylonitrile-butadiene rubber, typically 70 Shore A
- **Corrosion resistance:** Good resistance to mineral oil, grease and hydraulic fluid; poor in ozone and weathering
- **Magnetic response:** Non-magnetic
- **Service temperature:** approx. -30 °C to +100 °C

Property values are typical for the grade. Certified mechanical test data is available on request for production orders.

![NBR (Nitrile) Metric O-Rings (ISO 3601) reference image](https://engineeringhardware.com/wp-content/uploads/2026/09/Metric-O-Rings.webp)

NBR (Nitrile) (acrylonitrile-butadiene rubber, typically 70 Shore A) is the default elastomer for oil and hydraulic sealing. When metric o-rings (iso 3601) are specified in this grade, the dimensions remain per ISO 3601-1 (fluid power — O-rings, inside diameters and cross-sections); the material determines corrosion behavior (good resistance to mineral oil, grease and hydraulic fluid; poor in ozone and weathering) and the service temperature range (approx. -30 °C to +100 °C). Both are covered below with the size table.

## Why Choose NBR (Nitrile) for Metric O-Rings (ISO 3601)

The default elastomer for oil and hydraulic sealing. For metric o-rings (iso 3601), this matters when good resistance to mineral oil, grease and hydraulic fluid; poor in ozone and weathering is the primary requirement.

## Mechanical & Physical Properties

| Grade designation | acrylonitrile-butadiene rubber, typically 70 Shore A |
| --- | --- |
| Magnetic response | Non-magnetic |
| Service temperature | approx. -30 °C to +100 °C |
| Corrosion characteristic | Good resistance to mineral oil, grease and hydraulic fluid; poor in ozone and weathering |

## Galvanic & Galling Considerations

Galvanic and galling behavior do not apply to metric o-rings (iso 3601) in NBR (Nitrile) — the relevant compatibility questions are chemical: confirm the elastomer against the fluid, the temperature and any cleaning agents in service, and check the gland or groove dimensions give the intended compression on the section.

## Comparable Grades

For metric o-rings (iso 3601), consider FKM where temperature or chemical exposure is higher, or EPDM where the medium is water, steam or brake fluid rather than oil. Elastomer selection is decided by the medium, the temperature range and whether the seal is static or dynamic — not by strength.

## Sizes of Metric O-Rings (ISO 3601) Available in NBR (Nitrile)

| Cross-section (mm) | Typical inside-diameter range (mm) | Common compounds | Notes |
| --- | --- | --- | --- |
| 1.0 | 1.0 – 20 | NBR, FKM, EPDM, silicone | miniature and pneumatic |
| 1.5 | 2.0 – 40 | NBR, FKM, EPDM, silicone | small pneumatic and instrument |
| 1.78 | 1.78 – 50 | NBR, FKM, EPDM | nearest metric equivalent to the 1/16 in section |
| 2.0 | 3.0 – 100 | NBR, FKM, EPDM, silicone | general hydraulic and pneumatic |
| 2.5 | 5.0 – 150 | NBR, FKM, EPDM | general hydraulic |
| 3.0 | 6.0 – 200 | NBR, FKM, EPDM | general hydraulic |
| 3.5 | 10 – 250 | NBR, FKM | hydraulic |
| 4.0 | 12 – 300 | NBR, FKM | hydraulic and larger flanges |
| 5.0 | 20 – 400 | NBR, FKM | large flanges and covers |
| 5.33 | 20 – 400 | NBR, FKM | nearest metric equivalent to the 3/16 in section |
| 6.0 | 25 – 500 | NBR, FKM | large covers and housings |

Dimensions are independent of the material: every size above is available in NBR (Nitrile).

Custom manufacturing · Made to drawing

## Need this seal in a grade that is not listed?

Nbr is one of the grades the catalog describes. Inside diameter, cross-section and compound are the three that matter, and the compound is chosen against the fluid and the temperature rather than the dimensions.

Minimum order from 2,000 pieces; samples within 7 days of drawing approval.

[Custom seal manufacturing](https://engineeringhardware.com/custom/seals/)[Send a drawing](https://engineeringhardware.com/custom/seals/#rfq)

## Technical Drawing

Dimensioned line drawing of 1.0 Metric O-Rings (ISO 3601) to ISO 3601-1 (fluid power — O-rings, inside diameters and cross-sections). Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected.

- **Typical inside-diameter range (mm):** 1.0 – 20
- **Common compounds:** NBR, FKM, EPDM, silicone
- **Notes:** miniature and pneumatic

## Dimensions & Specifications (ISO 3601-1 (fluid power — O-rings, inside diameters and cross-sections))

| Cross-section (mm) | Typical inside-diameter range (mm) | Common compounds | Notes |
| --- | --- | --- | --- |
| 1.0 | 1.0 – 20 | NBR, FKM, EPDM, silicone | miniature and pneumatic |
| 1.5 | 2.0 – 40 | NBR, FKM, EPDM, silicone | small pneumatic and instrument |
| 1.78 | 1.78 – 50 | NBR, FKM, EPDM | nearest metric equivalent to the 1/16 in section |
| 2.0 | 3.0 – 100 | NBR, FKM, EPDM, silicone | general hydraulic and pneumatic |
| 2.5 | 5.0 – 150 | NBR, FKM, EPDM | general hydraulic |
| 3.0 | 6.0 – 200 | NBR, FKM, EPDM | general hydraulic |
| 3.5 | 10 – 250 | NBR, FKM | hydraulic |
| 4.0 | 12 – 300 | NBR, FKM | hydraulic and larger flanges |
| 5.0 | 20 – 400 | NBR, FKM | large flanges and covers |
| 5.33 | 20 – 400 | NBR, FKM | nearest metric equivalent to the 3/16 in section |
| 6.0 | 25 – 500 | NBR, FKM | large covers and housings |

Product catalog

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## Applications & Industries

Where Metric O-Rings are used, and what decides the specification in each case. Stocked from 1.0 to 6.0 (inside diameter).

### Industries that specify Metric O-Rings

- **Hydraulics:** Port, cover and piston seals.
- **Pneumatics:** Cylinder and valve seals.
- **Food and beverage:** EPDM and silicone compounds.
- **Chemical plant:** FKM for aggressive media.
- **Hydraulics & pneumatics:** Static and dynamic sealing in cylinders and valve bodies.
- **Process & food equipment:** Sealing at joints that are cleaned and inspected.

### Typical applications

- specifying inside diameter, cross-section and compound together
- matching the compound to the fluid and the temperature
- checking the groove dimensions give the right squeeze
- using a back-up ring at high pressure
- sealing a joint against fluid or air pressure
- excluding dust and moisture from a housing

### Service conditions to specify against

- **Sealed joints:** Used where the fixing has to keep water or air out as well as hold — the elastomer, not the fastener, decides service life.

### Where to use something else

- Do not substitute an NBR ring for an FKM one because the dimensions match; the size fits and the compound fails, which looks like a leak with no cause.

[Full application guide: where Metric O-Rings are used, how to specify them, and the cases they are wrong for](https://engineeringhardware.com/applications/metric-o-rings/)

Inside the plant

## Manufactured in our own plant

This part is cold-formed, threaded, heat-treated and finished in-house. The stages below are where its class and finish are actually decided.

1. ![Wire rod feeding into a cold heading machine](https://engineeringhardware.com/wp-content/uploads/2026/08/09-wire-rod-feed-cold-heading-machine.webp) 01 **Cold heading** Wire rod is drawn to size and cold-formed into blanks. Forming rather than cutting keeps the grain flow continuous around the head, which is where a bolt is most likely to fail. Head dimensions and under-head radius checked at set-up and per shift.
2. ![Thread rolling machine producing bolt threads](https://engineeringhardware.com/wp-content/uploads/2026/08/03-thread-rolling-machine-bolt-production.webp) 02 **Thread rolling** Threads are rolled between hardened dies rather than cut. Rolled threads are stronger in fatigue than cut threads and hold pitch and flank angle far more consistently across a batch. Go / no-go ring gauges to ISO 965 tolerance class 6g.
3. ![Baskets of bolts staged for heat treatment](https://engineeringhardware.com/wp-content/uploads/2026/08/05-heat-treatment-baskets-black-bolts.webp) 03 **Heat treatment** Quench-and-temper brings carbon and alloy steel to the property class ordered — 8.8, 10.9 or 12.9 — with the furnace charge tracked so a finished lot can be traced back to it. Core hardness and tensile tested per lot to ISO 898-1.
4. ![Zinc plated bolts in a treatment basket](https://engineeringhardware.com/wp-content/uploads/2026/08/23-zinc-plated-bolts-treatment-basket.webp) 04 **Surface treatment** Zinc, zinc-nickel, hot-dip galvanizing, black oxide, phosphate and Dacromet, selected against the service environment rather than against the price list. Coating thickness and neutral salt spray hours to ISO 9227.

## Frequently Asked Questions

### Which media is NBR (Nitrile) suitable for?

NBR (Nitrile) suits mineral oils, hydraulic fluids, greases and water. It is the wrong choice for ketones, brake fluid, ozone and strong acids. Elastomer selection is decided by the fluid first, then the temperature, then whether the seal is static or dynamic.

### What hardness are NBR (Nitrile) Metric O-Rings (ISO 3601) supplied in?

Shore A 70 is the general-purpose default. A softer compound (around 60) seals better on a rough or slightly out-of-round surface; a harder one (around 80 to 90) resists extrusion at higher pressure or across a wider gap. State the hardness on the order — it is not implied by the material.

### Does NBR (Nitrile) have a shelf life?

Yes. Elastomers age in storage as well as in service — keep them cool, dark, dry and away from ozone sources such as electric motors, and use stock in the order it arrived. PTFE is the exception and does not age this way.

### How much compression should NBR (Nitrile) metric o-rings (iso 3601) see?

The groove or gland decides it, not the seal: a static radial seal is normally designed for roughly 15–30% compression on the section, and a dynamic one for less. Give us the groove dimensions and the pressure and we will confirm the section against them.

### How do I request a quotation?

Use the technical drawing on this page to pick the exact configuration, then submit it with the quote form. We respond within one business day.

## Related Pages

[View the full Metric O-Rings (ISO 3601) page](https://engineeringhardware.com/fastener/metric-o-rings/)

### More Metric O-Rings (ISO 3601) Guides