Quick answer
Choose silicone o-rings for extreme temperatures and FDA compliance; choose Buna-N nitrile o-rings for oil resistance and general-purpose sealing at a lower cost.
Temperature range matters most
The operating temperature of your application is the first filter. Silicone handles from -80°F to +450°F, making it ideal for ovens, freezers, and outdoor equipment. Buna-N nitrile works from -40°F to +250°F, which covers most hydraulic and pneumatic systems but fails above that range.
Chemical and fluid exposure
Buna-N nitrile resists petroleum-based oils, fuels, and hydraulic fluids, so it is the standard choice for automotive and industrial sealing. Silicone has poor resistance to oils but performs well with dry heat, steam, and many chemicals like alcohols and dilute acids. If your seal contacts lubricants, Buna-N is usually the safer pick.
Compliance and color coding
FDA-compliant silicone o-rings are approved for food contact and pharmaceutical use. The red color in many silicone seals helps with visual identification during maintenance. Buna-N is not typically FDA-rated and is better suited for non-food applications.
O-ring material decision rules
- Check temperature range: If your application runs below -40°F or above +250°F, choose silicone. For moderate temperatures (-40°F to +250°F), Buna-N is sufficient and more economical.
- Evaluate chemical contact: If the seal touches petroleum oils, fuels, or hydraulic fluids, pick Buna-N nitrile. For dry heat, steam, or food-grade chemicals, silicone is the better choice.
- Confirm compliance needs: For food, beverage, or pharmaceutical contact, select an FDA-compliant silicone o-ring. For general industrial use without food contact, Buna-N works well. Verify the durometer (hardness) matches your groove design; 70 Shore A is the most common and works for most static and dynamic seals.
O-ring product comparison
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0.139" CS X 7.484" ID Silicone O-Rings | AS568-266 | Dash 266 | FDA Compliant | 70 Durometer | Red (16 / Pkg.): Silicone o-ring with AS568-266 size, 7.484" ID, 0.139" cross-section, 70 durometer, FDA compliant, red, service range -80°F to +450°F. This seal works in high-heat or food-contact environments where standard rubber would fail, and the red color simplifies inspection.
0.139" CS X 7.484" ID Silicone O-Rings | AS568-266 | Dash 266 | FDA Compliant | 70 Durometer | Red (16 / Pkg.)
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0.103" CS X 0.361" ID Buna-N Nitrile O-Rings | AS568-110 | Dash 110 | X-Ring | 70 Durometer (600 / Pkg.): Buna-N nitrile X-ring in AS568-110 size, 0.361" ID, 0.103" cross-section, 70 durometer, service range -40°F to +250°F. The X-ring profile reduces friction and extrusion in dynamic applications, and Buna-N resists oil and fuel better than silicone.
0.103" CS X 0.361" ID Buna-N Nitrile O-Rings | AS568-110 | Dash 110 | X-Ring | 70 Durometer (600 / Pkg.)
Which o-ring material fits your application?
Best for
- High-temperature or food-contact applications: silicone o-rings (e.g., AS568-266, FDA compliant)
- Oil-resistant, cost-effective sealing: Buna-N nitrile o-rings (e.g., AS568-110 X-ring)
Not for
- Applications above 250°F with oil exposure: choose silicone instead of Buna-N
- Food contact with oil resistance: choose an FDA-compliant FKM or PTFE seal