The complete guide to O-ring materials

  • Selo Technical Team
  • Reviewed August 2026
  • 14 min read

Quick answer

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Guide

PLACEHOLDER — Pillar intro paragraph before the first section.

How to choose

Start with the fluid your O-ring touches. Most seal failures we see come from a material that was never compatible in the first place, not from a faulty part. Then check the working temperature range, and finally the pressure and whether the joint is static or moving.

If you know your fluid, our material checker will point you to a recommendation in seconds. The sections below explain the why.

NBR (Nitrile)

Temp range: -30 to +100°C

The workhorse. Excellent with mineral oils, fuels, greases and hydraulic fluids at the lowest cost, which is why around 8 in 10 O-rings sold are NBR. Avoid it with ozone, sunlight, steam and brake fluid.

Shop NBR O-ringsRead the full NBR guide

FKM (Viton®)

Temp range: -20 to +200°C

The upgrade for heat and chemicals. Outstanding with fuels, oils and most chemicals at temperatures NBR can't touch. Costs more, so specify it when conditions demand it. Never use FKM with steam or hot water.

Shop FKM O-ringsRead the full FKM guide

EPDM

Temp range: -45 to +130°C

The water specialist. Excellent with water, steam, coolants and brake fluid. Keep it away from oils and fuels.

Shop EPDM O-rings

Silicone

Temp range: -60 to +200°C

The temperature extremist. Flexible from deep freeze to oven heat. Not for dynamic joints or fuels.

Shop silicone O-rings

Comparison

Material Temp range Oils & fuels Water & steam Weathering
NBR -30 to +100°C Excellent Limited Poor
FKM (Viton) -20 to +200°C Excellent Avoid steam Excellent
EPDM -45 to +130°C Avoid Excellent Excellent
Silicone -60 to +200°C Limited Limited Excellent

Working ranges for standard grades.

FAQs

See the FAQ accordion below.

Frequently asked questions

Is Viton® the same as FKM?
{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Yes. Viton® is DuPont's brand name for FKM fluoroelastomer. Any FKM O-ring of the same grade performs the same."}]}]}
What does Shore hardness mean?
{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"How firm the rubber is. Shore 70 is the standard for most O-rings; Shore 90 resists extrusion in high-pressure joints."}]}]}
Which material is food safe?
{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"FDA-grade silicone or EPDM. Standard NBR is not food safe. Look for the FDA marking on the product page."}]}]}

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