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AS568-250 O-Ring Size
200 series · 1/8" cross section · General purpose, cylinders
Inside diameter × cross section
126.59 × 3.53 mm
4.984″ × 0.139″ ·
outside diameter 133.65 mm (5.262″)
Dimensions
| Dimension | Inches | Millimetres |
|---|---|---|
| Inside diameter (ID) | 4.984″ | 126.59 mm |
| Cross section (CS) | 0.139″ | 3.53 mm |
| Outside diameter (OD) | 5.262″ | 133.65 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 126.59 mm, because compression set is permanent. If your measurement came in a little under this and the cross section roughly matches, -250 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) |
|---|---|---|---|
| -249 | 123.42 | 4.859″ | 130.48 |
| -251 | 129.77 | 5.109″ | 136.83 |
| -248 | 120.24 | 4.734″ | 127.3 |
| -252 | 132.94 | 5.234″ | 140.0 |