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AS568-261 O-Ring Size
200 series · 1/8" cross section · General purpose, cylinders
Inside diameter × cross section
171.04 × 3.53 mm
6.734″ × 0.139″ ·
outside diameter 178.1 mm (7.012″)
Dimensions
| Dimension | Inches | Millimetres |
|---|---|---|
| Inside diameter (ID) | 6.734″ | 171.04 mm |
| Cross section (CS) | 0.139″ | 3.53 mm |
| Outside diameter (OD) | 7.012″ | 178.1 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 171.04 mm, because compression set is permanent. If your measurement came in a little under this and the cross section roughly matches, -261 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) |
|---|---|---|---|
| -260 | 164.69 | 6.484″ | 171.75 |
| -262 | 177.39 | 6.984″ | 184.45 |
| -259 | 158.34 | 6.234″ | 165.4 |
| -263 | 183.74 | 7.234″ | 190.8 |