O-Ring Lexicon

ISO 3601 standard

ISO 3601 is the international standard for O-rings. It defines dimensions, tolerances and quality requirements for sealing rings and thereby creates worldwide comparability.

What is the ISO 3601 standard?

ISO 3601 is the authoritative international standard for O-rings. It is divided into several parts: Part 1 defines the inner diameters, cord thicknesses and their tolerances, Part 2 the housings and grooves for general applications, Part 3 the quality criteria, and Part 5 the material requirements for hydraulic and pneumatic applications. The standard thus sets out which dimensions are considered standardised and how tightly they must be maintained. In many areas it replaces older national standards and is today the common language between designer, manufacturer and buyer.

Why the ISO 3601 standard matters for O-rings

Anyone ordering to ISO 3601 knows exactly which dimensions and tolerances they will receive, regardless of supplier or country. This avoids mix-ups, makes second-source capability easier and ensures that groove and O-ring fit together. For design, the standard also provides the requirements for the installation space — that is, groove depth, groove width and compression. This means a seal can be designed to the standard consistently, from dimension selection through to the groove.

The key points at a glance

ISO 3601 is the international O-ring standard for dimensions, tolerances and quality.
It creates comparability across suppliers and countries.
It also sets the requirements for the installation space and the groove.

You'll find the standardised dimensions in our tables, and the associated tolerances under tolerances.

To the tolerances →