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AS568-279 O-Ring Size
200 series · 1/8" cross section · General purpose, cylinders
Inside diameter × cross section
329.79 × 3.53 mm
12.984″ × 0.139″ ·
outside diameter 336.85 mm (13.262″)
Dimensions
| Dimension | Inches | Millimetres |
|---|---|---|
| Inside diameter (ID) | 12.984″ | 329.79 mm |
| Cross section (CS) | 0.139″ | 3.53 mm |
| Outside diameter (OD) | 13.262″ | 336.85 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 329.79 mm, because compression set is permanent. If your measurement came in a little under this and the cross section roughly matches, -279 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 200 series
These share the same 1/8" 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) |
|---|---|---|---|
| -278 | 304.39 | 11.984″ | 311.45 |
| -280 | 355.19 | 13.984″ | 362.25 |
| -277 | 291.69 | 11.484″ | 298.75 |
| -276 | 278.99 | 10.984″ | 286.05 |