International standards

O-Ring Standards Reference

Understand the main O-ring size standards before using a dimensional cross-reference. A converted dimension is not automatically the same as a separately standardized size.

SAE AS568

United States / Aerospace & industrial

AS568 is an SAE size standard for O-rings using dash-number designations with nominal inside diameters and cross-sections.

Current revision: AS568F

ISO 3601-1

International

ISO 3601-1 specifies O-ring inside diameters, cross-sections, tolerances and designation codes for fluid power systems and general industrial / aerospace applications.

Current: 2012 edition + Amendment 1:2019

JIS B 2401-1

Japan

JIS B 2401-1 covers O-rings for general equipment, including P (moving), G (fixed) and V (vacuum flange) series, and specifies shapes, dimensions, appearance and materials.

Current: 2012 edition; confirmed 2026-06-22

BS 1806

United Kingdom / legacy imperial reference

BS 1806 is a British imperial O-ring size reference that includes sizes in several cross-section groups and additional intermediate sizes.

Superseded by BS ISO 3601; still referenced for cross-reference

Cross-reference caution: Cross-reference by dimension only unless the source explicitly establishes an equivalent designation. Tolerances, material, groove design, application and service conditions can prevent direct interchange.