JIS O-Ring Size Chart (JIS B 2401)

Japanese JIS O-rings are sealing components manufactured according to the JIS B 2401 O-ring sizing standard, which is widely used in Japan and across many Asian manufacturing industries. Like other international O-ring standards, JIS O-rings define specific dimensions for O-ring inside diameter (ID), cross section (CS), and reference outside diameter (OD). These dimensions ensure that rubber O-rings, elastomer seals, and gasket components will properly fit standardized sealing grooves used in machinery and equipment built to Japanese engineering specifications.

The primary difference between JIS O-rings and AS568 O-rings lies in the dimensional system and identification method used for each standard. AS568 O-rings typically use dash numbers to define size families, while JIS O-rings are identified by specific JIS size codes defined in the JIS B 2401 standard. These codes correspond to precise metric dimensions that align with equipment manufactured in Japan and other metric-based industrial systems.

Because many global industries use equipment built to different standards, engineers often encounter both AS568 O-rings and JIS O-rings in the same facility. Cross referencing between these systems helps ensure that the correct rubber O-rings, gasket seals, and elastomer components are selected when maintaining or repairing international equipment.

The JIS B 2401 standard provides a detailed framework for identifying and specifying Japanese O-ring sizes used in industrial sealing applications. The standard defines several important dimensional parameters including O-ring identification codes, cross section (CS), inside diameter (ID), and reference outside diameter (OD). These measurements allow engineers to select sealing components that properly fit metric sealing grooves and provide reliable compression for leak prevention.

The inside diameter (ID) represents the internal measurement of the rubber O-ring, while the cross section (CS) describes the thickness of the elastomer material that forms the circular sealing profile. Together, these two dimensions determine how the O-ring fits into a groove and how much compression is generated during installation. Proper compression is critical for ensuring that O-rings, rubber seals, and gasket components maintain an effective seal against liquids, gases, or vacuum environments.

Although outside diameter (OD) values are often listed in JIS O-ring charts, they are typically used only as reference dimensions. Compliance with the JIS B 2401 standard is defined primarily by the inside diameter and cross section, ensuring consistent performance for elastomer sealing components across industrial applications.

Japanese JIS O-rings can be manufactured using a wide range of elastomer materials designed for different chemical, thermal, and mechanical environments. Standard materials include NBR (nitrile), EPDM, silicone (VMQ), fluorosilicone (FVMQ), and FKM (Viton), each offering different performance characteristics depending on the application.

For highly demanding environments involving aggressive chemicals or extreme temperatures, perfluoroelastomers (FFKM) such as Kalrez®, Canrez®, and Chemraz® are often selected. These materials provide exceptional resistance to chemical attack, high temperatures, and plasma exposure, making them ideal for semiconductor manufacturing, chemical processing systems, pharmaceutical equipment, and aerospace applications.

Additional specialty sealing materials such as PTFE based seals or PTFE encapsulated O-rings may also be used when extremely low friction or superior chemical resistance is required. Engineers often review material datasheets, TDS documentation, test reports, and SDS information to verify chemical compatibility and confirm that the selected rubber O-ring or gasket compound will perform reliably in the intended operating conditions.

Japanese JIS O-rings are widely used in industries that rely on equipment manufactured in Japan or designed using Japanese engineering standards. These industries include automotive manufacturing, robotics, industrial automation, semiconductor fabrication, chemical processing, pharmaceutical production, and aerospace engineering.

Many Japanese manufacturers design pumps, valves, hydraulic systems, and precision equipment using JIS B 2401 O-ring dimensions. As a result, maintenance teams and engineers working with these systems often require replacement rubber O-rings, elastomer seals, and gasket components that match JIS specifications rather than AS568 or other international standards.

Because global manufacturing environments frequently combine equipment from multiple regions, facilities may use a mixture of JIS O-rings, metric O-rings, and AS568 O-rings. Having access to reliable sizing charts and cross reference resources helps engineers quickly identify compatible sealing components and maintain consistent system performance.

Identifying the correct JIS O-ring size usually involves referencing equipment drawings, manufacturer documentation, or maintenance specifications that list the JIS B 2401 size designation. These codes correspond to specific inside diameter and cross section values used for rubber O-rings and gasket seals designed for metric equipment.

If documentation is unavailable, engineers can also measure the original seal to determine the inside diameter and cross section of the O-ring. These measurements can then be compared against a JIS O-ring sizing chart to identify the correct standard size. Because precise sealing compression is required for reliable performance, accurate measurement is essential when selecting replacement elastomer components.

Engineers must also consider material compatibility, operating temperature, pressure, and chemical exposure when choosing a replacement O-ring. Selecting the correct rubber compound or high performance elastomer ensures that the seal will maintain its integrity and prevent leakage under demanding operating conditions.

Yes. Canyon Components supplies both standard JIS O-rings and custom O-ring solutions for applications that require specialized dimensions or materials. Standard JIS B 2401 O-ring sizes are available in a wide variety of elastomers including NBR, EPDM, silicone, fluorosilicone, FKM (Viton), and high performance FFKM materials such as Kalrez®, Canrez®, and Chemraz®.

For applications where standard sizes are not sufficient, custom molded O-rings, elastomer seals, and gasket components can be manufactured to match unique sealing groove designs. Custom solutions may include specialized cross sections, non-standard diameters, custom durometers, or materials engineered for extreme environments such as chemical processing plants or semiconductor manufacturing systems.

Canyon Components engineers can also assist with O-ring material selection, international sizing cross references, sealing design considerations, and compatibility analysis. Whether you require a standard JIS O-ring, an AS568 equivalent, or a custom rubber gasket solution, our engineering team can help identify the best sealing option for your application.