Contact Us Now
O-Ring Standards Overview
O-Ring Standards Overview
O-Ring standards define the dimensional sizes, tolerances, and performance requirements used across global sealing applications. Understanding the differences between international O-Ring standards is essential for engineers, OEMs, and procurement teams to ensure proper fit, sealing reliability, and interchangeability.
This page provides an overview of the most commonly used O-Ring standards, including AS568, ISO 3601, and DIN 3771, helping you quickly identify the correct specification for your application. Request a quote or navigate to detailed size charts for precise selection.
What Are O-Ring Standards?
O-Ring standards are internationally recognized specifications that define O-Ring inside diameter (ID), cross-section (CS), tolerances, and testing criteria. These standards ensure compatibility between sealing components and grooves across different manufacturers and industries.
While materials and compounds may vary, dimensional standards allow O-Rings to be reliably selected, replaced, and sourced globally for hydraulic, pneumatic, and industrial sealing systems.
Major O-Ring Standards
| Standard | Region | Key Features | Typical Applications |
|---|---|---|---|
| AS568 | USA | Imperial sizes, wide industry adoption | Hydraulic & pneumatic systems |
| ISO 3601 | International | Metric sizes, defined tolerances | Global OEM equipment |
| DIN 3771 | Europe | Metric-based, legacy DIN systems | Industrial machinery |
| JIS B2401 | Japan | Metric sizes, JIS groove compatibility | Japanese equipment |
AS568 O-Ring Standard
The AS568 standard is the most widely used O-Ring size system in North America. It defines inch-based O-Ring sizes identified by three-digit dash numbers (e.g., -214, -325), making it easy to specify and replace O-Rings in hydraulic and pneumatic systems.
AS568 O-Rings are commonly available in NBR, FKM, EPDM, Silicone, and other elastomer materials.
View AS568 O-Ring Size Chart →
ISO 3601 O-Ring Standard
ISO 3601 is an international metric standard that specifies O-Ring dimensions, tolerances, and quality grades. It is commonly used in global OEM equipment and export-oriented industrial systems.
ISO 3601 includes multiple tolerance classes, allowing engineers to select precision levels based on sealing performance and cost requirements.
DIN 3771 O-Ring Standard
DIN 3771 is a German standard historically used in European industrial equipment. While many DIN sizes overlap with ISO 3601, DIN 3771 is still referenced in legacy systems and technical drawings.
For new designs, ISO 3601 is often recommended, but DIN 3771 O-Rings remain widely available for replacement and maintenance.
Materials Available Across Standards
O-Ring standards define dimensions, not materials. The same standard size can be manufactured in various elastomer compounds depending on application requirements.
- NBR (Nitrile) – general-purpose sealing
- FKM (Viton®) – high temperature & chemical resistance
- EPDM – water, steam, and outdoor environments
- HNBR – enhanced mechanical strength
- Silicone – low-temperature flexibility
- FFKM – extreme chemical & thermal resistance
Custom & OEM Support
If standard sizes do not meet your requirements, we support custom O-Rings manufactured to your specified dimensions, materials, and tolerances. OEM and bulk orders are available for industrial production and maintenance programs.
- Custom ID / OD / cross-section
- Non-standard tolerances
- Material and hardness selection
- Small batch to high-volume production
Custom O-Rings Manufacturing →
Why Choose Our O-Rings
- Full coverage of major international standards
- Consistent dimensional control
- Material traceability on request
- Support for OEM and export projects
- Fast quotation and technical response
FAQ
Q1: Can AS568 O-Rings be replaced with ISO sizes?
AS568 and ISO 3601 use different measurement systems. Some sizes may be close, but direct substitution is not always recommended without verifying groove compatibility.
Q2: Do O-Ring standards define material properties?
No. Standards primarily define dimensions and tolerances. Material selection depends on temperature, pressure, and media compatibility.
Q3: Can you supply O-Rings to multiple standards in one order?
Yes. We support mixed-standard orders for OEMs and maintenance projects.
Request a Quote
Need help selecting the right O-Ring standard or size? Our technical team is ready to assist with drawings, specifications, and bulk pricing.