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AS568-221 O-Ring Size
200 series · 1/8" cross section · General purpose, cylinders
Inside diameter × cross section
36.09 × 3.53 mm
1.421″ × 0.139″ ·
outside diameter 43.15 mm (1.699″)
Dimensions
| Dimension | Inches | Millimetres |
|---|---|---|
| Inside diameter (ID) | 1.421″ | 36.09 mm |
| Cross section (CS) | 0.139″ | 3.53 mm |
| Outside diameter (OD) | 1.699″ | 43.15 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 36.09 mm, because compression set is permanent. If your measurement came in a little under this and the cross section roughly matches, -221 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) |
|---|---|---|---|
| -220 | 34.52 | 1.359″ | 41.58 |
| -222 | 37.69 | 1.484″ | 44.75 |
| -219 | 32.92 | 1.296″ | 39.98 |
| -218 | 31.34 | 1.234″ | 38.4 |