AS568-001 O-Ring — 0.029 × 0.040 in
The -001 is a 000 series size: a 0.040 in cord on a 0.029 in inside diameter, which is 1.02 mm on 0.74 mm. Its outside diameter is 0.109 in (2.77 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) | 0.029 | 0.74 |
| Cross-section d₂ (cord) | 0.040 | 1.02 |
| Outside diameter (reference) | 0.109 | 2.77 |
| Inside diameter tolerance | ±0.004 | ±0.1 |
| 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 AS568-001 is a dimension
The -001 is a lookup key. Its first digit — 0 — puts it in the 000 Series family, and the remaining two digits are its position inside that family counted upwards by inside diameter, which makes it number 1 of the 50 sizes here. Neither digit group carries a size: the -001 is 0.029 in on a 0.040 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.
This is one of the three sizes in the 000 series whose cord is thinner than the cord the family is named for — they are the first three dash numbers ever assigned, and they sit in the 000 series because they were numbered before the cord families settled.