AS568 900 Series O-Rings — Boss Gaskets
The 900 series is not a cord family. These are boss gaskets — the rings that seal the joint between a straight-thread tube fitting and the boss it screws into — and they are numbered in AS568 because the same standard fixes the port sizes they fit.
900 Serieswhat is in this family and where it ends
Their cords change from size to size, which is the visible difference from the other five families: there, one cord covers a whole range. Here the cord is chosen per port, and the dash number is tied to the tube outside diameter the port is cut for rather than to the seal's own geometry.
The numbering in this series is not continuous — some numbers inside its range are in neither table consulted. Those gaps are in the numbering, not in this page, and which numbers are absent is listed below rather than filled in.
That is why a boss gasket is not interchangeable with an O-ring of the same inside diameter from another family. The inside diameter may match to within a few thousandths and the cord will not, and a joint designed for one will not seal on the other.
This is 20 dash numbers, from the -901 at 0.185 in (4.7 mm) inside diameter to the -932 at 2.337 in (59.36 mm). Its cords are not one size: 0.056 in (1.42 mm), 0.064 in (1.63 mm), 0.072 in (1.83 mm), 0.078 in (1.98 mm), 0.082 in (2.08 mm), 0.087 in (2.21 mm), 0.097 in (2.46 mm), 0.116 in (2.95 mm) and 0.118 in (3 mm).
The numbering is not continuous: 12 numbers inside the -901 to -932 range are in neither source table — -915, -917, -919, -921, -922, -923, -925, -926, -927, -929, -930 and -931. They are absent from the tables, not withheld here, which is why they have no page.
All 20 sizesdash number, inside diameter, cord and tolerances
| Dash | ID (in) | ID (mm) | Cord (in) | Cord (mm) | ID tol. | Cord tol. |
|---|---|---|---|---|---|---|
| -901 | 0.185 | 4.7 | 0.056 | 1.42 | ±0.005 | ±0.003 |
| -902 | 0.239 | 6.07 | 0.064 | 1.63 | ±0.005 | ±0.003 |
| -903 | 0.301 | 7.65 | 0.064 | 1.63 | ±0.005 | ±0.003 |
| -904 | 0.351 | 8.92 | 0.072 | 1.83 | ±0.005 | ±0.003 |
| -905 | 0.414 | 10.52 | 0.072 | 1.83 | ±0.005 | ±0.003 |
| -906 | 0.468 | 11.89 | 0.078 | 1.98 | ±0.005 | ±0.003 |
| -907 | 0.530 | 13.46 | 0.082 | 2.08 | ±0.007 | ±0.003 |
| -908 | 0.644 | 16.36 | 0.087 | 2.21 | ±0.009 | ±0.003 |
| -909 | 0.706 | 17.93 | 0.097 | 2.46 | ±0.009 | ±0.003 |
| -910 | 0.755 | 19.18 | 0.097 | 2.46 | ±0.009 | ±0.003 |
| -911 | 0.863 | 21.92 | 0.116 | 2.95 | ±0.009 | ±0.004 |
| -912 | 0.924 | 23.47 | 0.116 | 2.95 | ±0.009 | ±0.004 |
| -913 | 0.986 | 25.04 | 0.116 | 2.95 | ±0.010 | ±0.004 |
| -914 | 1.047 | 26.59 | 0.116 | 2.95 | ±0.010 | ±0.004 |
| -916 | 1.171 | 29.74 | 0.116 | 2.95 | ±0.010 | ±0.004 |
| -918 | 1.355 | 34.42 | 0.116 | 2.95 | ±0.012 | ±0.004 |
| -920 | 1.475 | 37.47 | 0.118 | 3 | ±0.014 | ±0.004 |
| -924 | 1.720 | 43.69 | 0.118 | 3 | ±0.014 | ±0.004 |
| -928 | 2.090 | 53.09 | 0.118 | 3 | ±0.018 | ±0.004 |
| -932 | 2.337 | 59.36 | 0.118 | 3 | ±0.018 | ±0.004 |
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.
Tolerances are the per-size figures the standard gives, not a value derived from the diameter — the same inside diameter can carry a different tolerance in a different series, and each page prints its own.
Reading a 9xx dash numberwhat the digits do and do not tell you
Every dash number in this family starts with the digit 9, which is what puts it here. The remaining two digits are its position in the family, counted upwards by inside diameter — they are not a size code, and nothing in them can be multiplied or read off to get a dimension. Two rings whose numbers differ by one can differ by a hundredth of an inch or by a quarter of one.
This is not a cord family. The digit 9 selects the branch of AS568 that fixes port sizes rather than seal sizes, so the cord is a consequence of the port a ring is specified for. That is why the cord changes from size to size here and does not in the five cord families.