AS568-902 O-Ring — 0.239 × 0.064 in
The -902 is a 900 series size: a 0.064 in cord on a 0.239 in inside diameter, which is 1.63 mm on 6.07 mm. Its outside diameter is 0.367 in (9.32 mm), derived as ID + 2 × cord.
Dimensionsthe two cells the standard fixes, and one derived value
| Dimension | Inches (AS568) | Millimetres (converted) |
|---|---|---|
| Inside diameter d₁ (ID) | 0.239 | 6.07 |
| Cross-section d₂ (cord) | 0.064 | 1.63 |
| Outside diameter (reference) | 0.367 | 9.32 |
| Inside diameter tolerance | ±0.005 | ±0.13 |
| Cross-section tolerance | ±0.003 | ±0.08 |
Inches are the standard’s own units; millimetre values are conversions — inch × 25.4, rounded to two decimals — and not the ISO 3601-1 metric sizes. Outside diameter is a reference value derived as ID + 2 × cross-section; the two diameters the standard fixes are the inside diameter and the cord.
Reading the designationnothing in AS568-902 is a dimension
The -902 is a lookup key. Its first digit — 9 — puts it in the 900 Series family, and the remaining two digits are its position inside that family counted upwards by inside diameter, which makes it number 2 of the 20 sizes here. Neither digit group carries a size: the -902 is 0.239 in on a 0.064 in cord, and a dash number one away from it can differ by a hundredth of an inch or by a quarter of one.
This is a 900-series boss gasket, not an O-ring for a groove: it seals the joint between a straight-thread tube fitting and the boss it screws into, and its dash number follows the tube the port is cut for rather than the seal’s own geometry. Its cord is 0.064 in, which is one of 9 cord sizes used across this series — the 900 series is not a cord family.
The same inside diameter, in another seriesa matching bore does not make two rings interchangeable
| Series | Dash | Cord (in) | Cord (mm) | ID tol. |
|---|---|---|---|---|
| 900 Series | -902 | 0.064 | 1.63 | ±0.005 |
| 000 Series | -010 | 0.070 | 1.78 | ±0.005 |
These rings share an inside diameter and nothing else. The cords differ, and so do the inside diameter tolerances on some of them — the tolerance is a per-size figure in the standard, not a function of the diameter, so it is printed rather than derived.