O-Rings
ISO 3601 O-Rings — International Metric Standard
ISO 3601 is the international standard governing O-Ring dimensions, tolerances and quality acceptance criteria. ISO 3601-1 defines dimensional tolerances for metric O-Rings; ISO 3601-2 covers quality acceptance criteria; ISO 3601-3 defines design guidance for glands. FITCO manufactures to ISO 3601 tolerance class A (tighter) and tolerance class B (general purpose) across the full metric CS/ID range.
| Tolerance Class | Application |
|---|---|
| ISO 3601 Class A | Tight tolerance — aerospace and critical sealing applications |
| ISO 3601 Class B | General purpose — standard industrial and commercial sealing |
ISO 3601 and AS568 are not directly interchangeable — they define different tolerances at similar nominal sizes. If your drawing references ISO 3601, specify the size as ID × CS in millimetres. FITCO will confirm the tolerance class on quotation.
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