AS568-389 O-Ring Size
Nominal free-state dimensions for the AS568-389 dash number, shown in both inch and millimetre units.
AS568-389 dimensions at a glance
The millimetre values are conversions of the nominal inch dimensions. They are not automatically equivalent to a metric-standard O-ring.
What do ID, CS and OD mean?
ID is the inside diameter. CS is the round cross-section of the cord. OD is the outside diameter.
OD calculation
OD = ID + 2 × CS
19.9550 + 2 × 0.210 = 20.3750 in
Do not assume interchangeability
A dimensional match is not enough to approve a replacement. Check the applicable standard, tolerances, compound, hardness, temperature, pressure, media and gland geometry.
Closest JIS B 2401 P-series dimension
149.6 × 5.7 × 161.0 mm
Closest dimensional match within the verified JIS P subset. This is not a claim of standards equivalence or interchangeability.
Nearby AS568 sizes
Nearby dash numbers are useful for identification, but they are not automatic replacement recommendations.
Browse the 309-395 series
This size belongs to the 309-395 cross-section family. Browse the complete series to compare its available dash numbers.
View 309-395 series87 sizes are listed in this series.
Find this size by measurement
Have an unmarked ring? Use inside diameter and cross-section to find the closest AS568 dash number.
Open size finderHow to measure an O-ring
Measure the ring relaxed and avoid squeezing or stretching the elastomer.
Measurement guideSource & scope
AS568 is an SAE Aerospace Standard specifying O-ring inside diameters, cross-sections, tolerances and dash-number identification. This site presents nominal dimensional reference data and does not certify a seal or approve a replacement.