Dimensional standards
What are dimensional standards?
A dimensional standard is a defined grid of inner diameters and cord thicknesses. It ensures that an O-ring can be uniquely identified and reordered with the same geometry regardless of the manufacturer. Two major systems are in common use internationally: the metric series according to ISO 3601, in which inner diameters and cord thicknesses are specified in millimeters, and the inch-based series according to AS568, which is widely used in the U.S. market. In addition, there are older national series such as DIN 3771, the content of which has now largely been incorporated into ISO 3601.
Why Dimensional Standards Are Important for O-Rings
For designers and buyers, a standard provides clarity. Anyone who specifies an O-ring according to ISO 3601 or AS568 describes its geometry without leaving room for misunderstanding. This prevents incorrect orders, simplifies groove design, and ensures that replacement parts remain reproducible for years to come. Particular care is required when converting between inch and metric series: An inch cross-section rarely corresponds exactly to a metric value, so it’s worth consulting the table before making any substitutions.
- Dimensional standards define the inner diameter and cord thickness according to a fixed grid.
- ISO 3601 applies to metric systems, AS568 applies to imperial systems, and DIN 3771 has largely been incorporated into the ISO standard.
- A clear standard prevents incorrect orders and ensures that replacement parts are consistent.
You can find the complete sets of dimensions in our O-ring tables. Please refer to the corresponding overview for the applicable tolerances.
Become a customer and gain access to over 30,000 sizes in stock.