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AS568-381 O-Ring Size
300 series · 3/16" cross section · Heavy hydraulics, higher pressure
Inside diameter × cross section
304.16 × 5.33 mm
11.975″ × 0.21″ ·
outside diameter 314.83 mm (12.395″)
Dimensions
| Dimension | Inches | Millimetres |
|---|---|---|
| Inside diameter (ID) | 11.975″ | 304.16 mm |
| Cross section (CS) | 0.21″ | 5.33 mm |
| Outside diameter (OD) | 12.395″ | 314.83 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 304.16 mm, because compression set is permanent. If your measurement came in a little under this and the cross section roughly matches, -381 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) |
|---|---|---|---|
| -380 | 291.46 | 11.475″ | 302.13 |
| -379 | 278.76 | 10.975″ | 289.43 |
| -382 | 329.56 | 12.975″ | 340.23 |
| -378 | 266.06 | 10.475″ | 276.73 |