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AS568-338 O-Ring Size
300 series · 3/16" cross section · Heavy hydraulics, higher pressure
Inside diameter × cross section
78.74 × 5.33 mm
3.1″ × 0.21″ ·
outside diameter 89.41 mm (3.52″)
Dimensions
| Dimension | Inches | Millimetres |
|---|---|---|
| Inside diameter (ID) | 3.1″ | 78.74 mm |
| Cross section (CS) | 0.21″ | 5.33 mm |
| Outside diameter (OD) | 3.52″ | 89.41 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 78.74 mm, because compression set is permanent. If your measurement came in a little under this and the cross section roughly matches, -338 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) |
|---|---|---|---|
| -337 | 75.56 | 2.975″ | 86.23 |
| -339 | 81.91 | 3.225″ | 92.58 |
| -336 | 72.39 | 2.85″ | 83.06 |
| -340 | 85.09 | 3.35″ | 95.76 |