ISO 3601 Metric O-Rings Size Chart

Issued by the International Organization for Standardization, the ISO 3601 standard contains of two groups of O-Rings, Class A and Class B. Class A corresponds to the American standard AS 568B in its current format (the 900 series tube fitting O-Rings are not included). The ISO 3601-1 Size Code for these O-Rings is the same as the AS 568 dash number. Class B allows production of O-Rings in technically acceptable and economical “metric” sizes, which can then fit into metric grooves. The first digit of the Size Code indicates the cross section group (A-E), while the last four digits indicate the O-Ring inside diameter rounded to one-tenth millimeter.

For a complete listing of all metric o-ring sizes, visit our Metric O-Ring Cross Reference Table.


ISO 3601 Size Chart

Global Part # Reference C/S (MM) I.D. (MM) C/S (Inch) I.D. (Inch)