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AS568-351 O-Ring Size
300 series · 3/16" cross section · Heavy hydraulics, higher pressure
Inside diameter × cross section
120.01 × 5.33 mm
4.725″ × 0.21″ ·
outside diameter 130.68 mm (5.145″)
Dimensions
| Dimension | Inches | Millimetres |
|---|---|---|
| Inside diameter (ID) | 4.725″ | 120.01 mm |
| Cross section (CS) | 0.21″ | 5.33 mm |
| Outside diameter (OD) | 5.145″ | 130.68 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 120.01 mm, because compression set is permanent. If your measurement came in a little under this and the cross section roughly matches, -351 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) |
|---|---|---|---|
| -350 | 116.84 | 4.6″ | 127.51 |
| -352 | 123.19 | 4.85″ | 133.86 |
| -349 | 113.66 | 4.475″ | 124.33 |
| -353 | 126.36 | 4.975″ | 137.03 |