ISO 3601-2:2025

This document specifies the housing dimensions for class A O-rings for general industrial applications conforming to ISO 3601-1, as well as housing dimensions for class B O-rings used on selected metric-dimensioned hardware, e.g. fluid power cylinder bores and piston rods. These O-rings are for use in general hydraulic and pneumatic applications without and with anti-extrusion rings (back-up rings). The dimensions of the O-rings (d1 and d2), size codes (SC) and tolerances conform to ISO 3601-1.
This document also addresses different design approaches in industry, and this is reflected in the table structures for hardware dimensions. Using the O-ring as a starting point to design the optimal hardware dimensions is reflected in  REF Table_tab_3 \r \h Tables 3
08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000C0000005400610062006C0065005F007400610062005F0033000000
,  REF Table_tab_5 \r \h 5
08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000C0000005400610062006C0065005F007400610062005F0035000000
, and  REF Table_tab_8 \r \h 8
08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000C0000005400610062006C0065005F007400610062005F0038000000
. Using fixed hardware dimensions (i.e. bore/rod) and choosing the most appropriate O-ring to fit is reflected in  REF Table_tab_4 \r \h Tables 4
08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000C0000005400610062006C0065005F007400610062005F0034000000
and  REF Table_tab_6 \r \h 6
08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000C0000005400610062006C0065005F007400610062005F0036000000
.
Housing dimensions for the O-rings intended for aerospace applications that are specified in ISO 3601-1 are addressed in  REF Annex_sec_A \r \h Annex A
08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000C00000041006E006E00650078005F007300650063005F0041000000
.
NOTE 1        It is expected that O-ring housing dimensions for special applications be agreed upon between the O-ring manufacturer and the user.
NOTE 2        The term “housing”, in this document, is used to describe the groove or cavity, into which the O-ring is fitted, and the mating surface, which between them confine the O-ring.