# What Is the Difference Between 70 and 90 O-Rings?

Confused about whether to choose a 70 or 90 O-ring for your project? Using the wrong hardness can lead to leaks, extrusion, or premature failure. The main difference between 70 and 90 O-rings is hardness. A 70-durometer O-ring is softer and more flexible, while a 90-durometer O-ring is harder and more resistant to extrusion under pressure. 70 vs 90 durometer O-ring Let’s explore how these hardness levels affect sealing performance, durability, and ideal use cases. What Does “Durometer” Mean in O-Rings? Not sure what the numbers 70 or 90 actually refer to? Durometer measures the hardness of rubber on the Shore A scale. A higher number means a harder material. 70A is standard for most O-rings, while 90A is for high-pressure or high-wear environments. ✅ Key Shore A Hardness Reference: Durometer1 Feel (Touch) Flexibility2 Typical Use 40A Very soft (gel-like) Very flexible Low-pressure static seals 70A Medium firmness ✅ Good flexibility Standard O-ring3 for most uses 90A Very firm ✅ Low flexibility High-pressure hydraulic/pneumatics 70 Durometer O-Rings: Why They're Most Common Looking for a general-purpose seal? 70A durometer O-rings are the industry standard for most sealing applications due to their balance of flexibility, compression set resistance, and media compatibility. 70A standard O-rings ✅ Benefits of 70A O-Rings: Easy to compress into sealing grooves Good sealing with low to moderate pressure4 Ideal for static and slow-moving dynamic seals5 Cost-effective and widely available6 Available in materials like NBR, FKM, EPDM, HNBR, Silicone ✅ Ideal For: Plumbing fittings HVAC systems Automotive fuel and oil lines Water-resistant enclosures General-purpose hydraulic seals 90 Durometer O-Rings: When to Choose Harder Rubber Need a seal that won’t get extruded under high pressure? 90A durometer O-rings are stiffer and stronger, making them suitable for high-pressure environments where extrusion or deformation is a concern. ✅ Benefits of 90A O-Rings: High resistance to extrusion7 Better wear and abrasion resistance Good dimensional stability under load8 Less prone to rolling or distortion in dynamic applications ✅ Ideal For: Hydraulic cylinders and pistons High-pressure valve stems Pneumatic actuators Heavy machinery and industrial systems ⚠️ Note: They require more compression force and are less forgiving in poorly machined grooves. 70 vs 90 O-Rings: Performance Comparison Here’s a quick look at how the two durometers differ across key performance factors. Property 70 Durometer ✅ 90 Durometer ✅ Hardness (Shore A) Medium High Flexibility Good ✅ Low ⚠️ Extrusion Resistance Moderate ⚠️ Excellent ✅ Compression Force Needed Low ✅ High ⚠️ Best For General sealing High-pressure sealing9 Groove Fill/Conformity Better ✅ Stiffer ⚠️ Which Durometer Should You Choose? Not sure which is right for your application? ✅ Choose 70 Durometer10 When: Dealing with static or slow-moving parts Groove dimensions may vary Sealing low to moderate pressure fluids You need a flexible, easy-to-install seal ✅ Choose 90 Durometer11 When: Operating in high-pressure hydraulic or pneumatic systems Extrusion risk is high (wide gaps, sharp edges) Wear resistance is critical The seal is exposed to repetitive movement or pressure spikes Conclusion 70-durometer O-rings are the best choice for most standard sealing needs, offering flexibility and sealing efficiency. 90-durometer O-rings are ideal for high-pressure, high-wear environments where extrusion resistance matters most. Always match hardness with pressure, fluid, and application conditions. 🔧 Need Help Choosing the Right O-Ring Hardness? Contact Julong Rubber or Request a Quote for custom durometer O-rings made to fit your specifications. Or message us now via WhatsApp: Understanding Durometer is essential for selecting the right material for your project. Explore this link for detailed insights. ↩ Flexibility is a key factor in material performance. Discover more about its importance in engineering applications. ↩ O-rings are crucial in sealing applications. Learn more about their uses and benefits in various industries. ↩ Understanding the advantages of effective sealing can enhance your application of O-Rings in various systems. ↩ Learning about the specific applications of O-Rings can optimize their use in your engineering designs. ↩ Exploring this topic can help you make informed decisions about O-Ring selection for your projects. ↩ Understanding the benefits of high extrusion resistance can help you choose the right O-Rings for your applications. ↩ Explore why dimensional stability is crucial for O-Rings to ensure reliable performance in various applications. ↩ Learn about the advantages of using 90 durometer O-Rings for high-pressure sealing to enhance your system's efficiency. ↩ Explore this link to understand the specific applications and benefits of using 70 Durometer seals in various scenarios. ↩ Discover the advantages of 90 Durometer seals, especially in high-pressure environments, to enhance your sealing solutions. ↩

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Generated: 2026-05-12T15:36:21+00:00