AS568-137 O-Ring — 2.050 × 0.103 in
The -137 is a 100 series size: a 0.103 in cord on a 2.050 in inside diameter, which is 2.62 mm on 52.07 mm. Its outside diameter is 2.256 in (57.3 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) | 2.050 | 52.07 |
| Cross-section d₂ (cord) | 0.103 | 2.62 |
| Outside diameter (reference) | 2.256 | 57.3 |
| Inside diameter tolerance | ±0.017 | ±0.43 |
| 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 AS568-137 is a dimension
The -137 is a lookup key. Its first digit — 1 — puts it in the 100 Series family, and the remaining two digits are its position inside that family counted upwards by inside diameter, which makes it number 36 of the 77 sizes here. Neither digit group carries a size: the -137 is 2.050 in on a 0.103 in cord, and a dash number one away from it can differ by a hundredth of an inch or by a quarter of one.