RUBRINGS / SELECTION & SUPPLY
O-ring standards & size systems
Compare AS568, AS568A, DIN 3771, BS 1806 and JIS references. Understand metric and imperial O-ring sizes before selecting a replacement.
AS568 O-rings & AS568A references
AS568 O-rings are identified by dash numbers in an American size system. For American standard O-rings, state the exact designation, revision, dimensions and material requirements.
AS568A O-rings may appear on older drawings. The suffix is part of the reference: do not silently replace a historical designation with another revision without checking the design requirements.
DIN 3771 O-rings
DIN 3771 appears in legacy German O-ring specifications. Provide the drawing, size and edition and have the applicable DIN/ISO requirements checked before substitution.
A metric measurement alone does not prove compliance with a DIN reference. The website does not publish a complete DIN tolerance or groove table.
BS 1806 O-rings & British standard references
For British standard O-rings, include the full BS designation and size code. BS 1806, BS 4518 and a legacy drawing reference should not be treated as interchangeable labels.
If your document says BS 1516 or another older reference, share the original drawing or chart so the designation can be verified. Compare actual dimensions and tolerances before agreeing on a replacement.
JIS O-rings
For JIS O-rings, retain the B 2401 reference and series prefix. The P and G series entries in our nominal chart are identified separately.
Metric O-rings, imperial O-rings and standard sizes
Metric O-rings are specified in millimetres. Imperial O-rings may be identified through an inch-based standard series even when a catalogue displays converted metric dimensions.
Standard O-ring sizes and metric O-ring sizes are not two universally interchangeable lists. Keep the size code and its source with ID × CS, and check the tolerances before substitution.
O-ring size standards: what to record
- Standard designation, edition and size code
- Nominal ID and cross-section, with units
- Applicable tolerance or quality class and drawing revision
- Compound, hardness and application requirements
O-ring standards describe particular requirements; naming a standard does not certify a supplied part. Confirm the supporting evidence for your order.
Reference catalogues: Trelleborg technical literature. Consult the current issuing standard for controlled requirements.
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