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AS568-209 O-Ring Size
200 series · 1/8" cross section · General purpose, cylinders
Inside diameter × cross section
17.04 × 3.53 mm
0.671″ × 0.139″ ·
outside diameter 24.1 mm (0.949″)
Dimensions
| Dimension | Inches | Millimetres |
|---|---|---|
| Inside diameter (ID) | 0.671″ | 17.04 mm |
| Cross section (CS) | 0.139″ | 3.53 mm |
| Outside diameter (OD) | 0.949″ | 24.1 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 17.04 mm, because compression set is permanent. If your measurement came in a little under this and the cross section roughly matches, -209 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) |
|---|---|---|---|
| -208 | 15.47 | 0.609″ | 22.53 |
| -210 | 18.64 | 0.734″ | 25.7 |
| -207 | 13.87 | 0.546″ | 20.93 |
| -211 | 20.22 | 0.796″ | 27.28 |