AS568-103 O-Ring — 0.081 × 0.103 in
The -103 is a 100 series size: a 0.103 in cord on a 0.081 in inside diameter, which is 2.62 mm on 2.06 mm. Its outside diameter is 0.287 in (7.29 mm), derived as ID + 2 × cord. Its inside diameter is smaller than the cord is thick, so almost nothing is left in the middle of the ring.
Dimensionsthe two cells the standard fixes, and one derived value
| Dimension | Inches (AS568) | Millimetres (converted) |
|---|---|---|
| Inside diameter d₁ (ID) | 0.081 | 2.06 |
| Cross-section d₂ (cord) | 0.103 | 2.62 |
| Outside diameter (reference) | 0.287 | 7.29 |
| 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 AS568-103 is a dimension
The -103 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 2 of the 77 sizes here. Neither digit group carries a size: the -103 is 0.081 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.
Worth knowing before you order one: this ring’s inside diameter is smaller than its cord is thick. It exists because a cord family is numbered by cord, and it is not a size to substitute for anything else on a bore dimension alone.