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AS568-331 O-Ring Size
300 series · 3/16" cross section · Heavy hydraulics, higher pressure
Inside diameter × cross section
56.52 × 5.33 mm
2.225″ × 0.21″ ·
outside diameter 67.18 mm (2.645″)
Dimensions
| Dimension | Inches | Millimetres |
|---|---|---|
| Inside diameter (ID) | 2.225″ | 56.52 mm |
| Cross section (CS) | 0.21″ | 5.33 mm |
| Outside diameter (OD) | 2.645″ | 67.18 mm |
Outside diameter is not measured, it is derived: OD = ID + 2 × CS.
If your measured OD disagrees with this, trust the ID and cross section — measuring
across the outside of a flexible ring is the least reliable of the three.
If you measured a used one
A ring pulled out of service will measure smaller than 56.52 mm, because compression set is permanent. If your measurement came in a little under this and the cross section roughly matches, -331 is very likely still the correct part. Ordering the size your worn ring measures is how the same failure repeats. More on this →
Nearby sizes in the 300 series
These share the same 3/16" cross section, so if the thickness is right but the diameter is off, your ring is probably one of these.
| Dash | ID (mm) | ID (in) | OD (mm) |
|---|---|---|---|
| -330 | 53.34 | 2.1″ | 64.01 |
| -332 | 59.69 | 2.35″ | 70.36 |
| -329 | 50.16 | 1.975″ | 60.83 |
| -333 | 62.87 | 2.475″ | 73.53 |