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AS568-253 O-Ring Size
200 series · 1/8" cross section · General purpose, cylinders
Inside diameter × cross section
136.12 × 3.53 mm
5.359″ × 0.139″ ·
outside diameter 143.18 mm (5.637″)
Dimensions
| Dimension | Inches | Millimetres |
|---|---|---|
| Inside diameter (ID) | 5.359″ | 136.12 mm |
| Cross section (CS) | 0.139″ | 3.53 mm |
| Outside diameter (OD) | 5.637″ | 143.18 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 136.12 mm, because compression set is permanent. If your measurement came in a little under this and the cross section roughly matches, -253 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) |
|---|---|---|---|
| -252 | 132.94 | 5.234″ | 140.0 |
| -254 | 139.29 | 5.484″ | 146.35 |
| -251 | 129.77 | 5.109″ | 136.83 |
| -255 | 142.47 | 5.609″ | 149.53 |