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AS568-378 O-Ring Size
300 series · 3/16" cross section · Heavy hydraulics, higher pressure
Inside diameter × cross section
266.06 × 5.33 mm
10.475″ × 0.21″ ·
outside diameter 276.73 mm (10.895″)
Dimensions
| Dimension | Inches | Millimetres |
|---|---|---|
| Inside diameter (ID) | 10.475″ | 266.06 mm |
| Cross section (CS) | 0.21″ | 5.33 mm |
| Outside diameter (OD) | 10.895″ | 276.73 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 266.06 mm, because compression set is permanent. If your measurement came in a little under this and the cross section roughly matches, -378 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) |
|---|---|---|---|
| -377 | 253.36 | 9.975″ | 264.03 |
| -379 | 278.76 | 10.975″ | 289.43 |
| -376 | 247.01 | 9.725″ | 257.68 |
| -375 | 240.66 | 9.475″ | 251.33 |