ORB Boss O-Ring Size Chart (AS568 900-Series)
AS568 900-series ORB boss O-Ring size chart for SAE J1926 ports: dash, tube OD, thread, ID, CS, and OD, plus how boss seals fit the AS568 and J1926 story.
History of ORB boss seals ORB Boss O-Rings guide Shop Hydraulic Boss O-Rings
ORB boss O-Rings are the AS568 900-series seals for SAE J1926 O-Ring Boss ports. They are not the same as standard 0xx–4xx face or radial O-Rings. Threads clamp the fitting; the 9xx O-Ring seals in the port chamfer.
These are AS568 900-series boss seals for SAE J1926 ORB (O-Ring Boss) ports—not the 0xx–4xx face/radial dashes. OD = ID + 2×CS. Code links open a product search on theoringstore.com. Interactive filter: Master O-Ring Size Chart → ORB Boss. Full port write-up: SAE J1926 ORB Boss O-Rings.
| Dash | Code | ORB dash | Tube OD | Thread (UN/UNF) | ID (in) | CS (in) | OD (in) | ID (mm) | CS (mm) | OD (mm) |
|---|---|---|---|---|---|---|---|---|---|---|
| -901 | AS568-901 | — | 3/32 | — | 0.185 ±.005 | 0.056 ±.003 | 0.297 | 4.70 ±0.13 | 1.42 ±0.08 | 7.54 |
| -902 | AS568-902 | -2 | 1/8 | 5/16-24 | 0.239 ±.005 | 0.064 ±.003 | 0.367 | 6.07 ±0.13 | 1.63 ±0.08 | 9.33 |
| -903 | AS568-903 | -3 | 3/16 | 3/8-24 | 0.301 ±.005 | 0.064 ±.003 | 0.429 | 7.65 ±0.13 | 1.63 ±0.08 | 10.91 |
| -904 | AS568-904 | -4 | 1/4 | 7/16-20 | 0.351 ±.005 | 0.072 ±.003 | 0.495 | 8.92 ±0.13 | 1.83 ±0.08 | 12.58 |
| -905 | AS568-905 | -5 | 5/16 | 1/2-20 | 0.414 ±.005 | 0.072 ±.003 | 0.558 | 10.52 ±0.13 | 1.83 ±0.08 | 14.18 |
| -906 | AS568-906 | -6 | 3/8 | 9/16-18 | 0.468 ±.005 | 0.078 ±.003 | 0.624 | 11.89 ±0.13 | 1.98 ±0.08 | 15.85 |
| -907 | AS568-907 | -7 | 7/16 | 5/8-18 | 0.530 ±.007 | 0.082 ±.003 | 0.694 | 13.46 ±0.18 | 2.08 ±0.08 | 17.62 |
| -908 | AS568-908 | -8 | 1/2 | 3/4-16 | 0.644 ±.009 | 0.087 ±.003 | 0.818 | 16.36 ±0.23 | 2.21 ±0.08 | 20.78 |
| -909 | AS568-909 | — | 9/16 | — | 0.706 ±.009 | 0.097 ±.003 | 0.900 | 17.93 ±0.23 | 2.46 ±0.08 | 22.85 |
| -910 | AS568-910 | -10 | 5/8 | 7/8-14 | 0.755 ±.009 | 0.097 ±.003 | 0.949 | 19.18 ±0.23 | 2.46 ±0.08 | 24.10 |
| -911 | AS568-911 | — | 11/16 | — | 0.863 ±.009 | 0.116 ±.004 | 1.095 | 21.92 ±0.23 | 2.95 ±0.10 | 27.82 |
| -912 | AS568-912 | -12 | 3/4 | 1-1/16-12 | 0.924 ±.009 | 0.116 ±.004 | 1.156 | 23.47 ±0.23 | 2.95 ±0.10 | 29.37 |
| -913 | AS568-913 | — | 13/16 | — | 0.986 ±.010 | 0.116 ±.004 | 1.218 | 25.04 ±0.26 | 2.95 ±0.10 | 30.94 |
| -914 | AS568-914 | -14 | 7/8 | 1-3/16-12 | 1.047 ±.010 | 0.116 ±.004 | 1.279 | 26.59 ±0.26 | 2.95 ±0.10 | 32.49 |
| -916 | AS568-916 | -16 | 1 | 1-5/16-12 | 1.171 ±.010 | 0.116 ±.004 | 1.403 | 29.74 ±0.26 | 2.95 ±0.10 | 35.64 |
| -918 | AS568-918 | — | 1-1/8 | — | 1.355 ±.012 | 0.116 ±.004 | 1.587 | 34.42 ±0.30 | 2.95 ±0.10 | 40.32 |
| -920 | AS568-920 | -20 | 1-1/4 | 1-5/8-12 | 1.475 ±.014 | 0.118 ±.004 | 1.711 | 37.47 ±0.36 | 3.00 ±0.10 | 43.47 |
| -924 | AS568-924 | -24 | 1-1/2 | 1-7/8-12 | 1.720 ±.014 | 0.118 ±.004 | 1.956 | 43.69 ±0.36 | 3.00 ±0.10 | 49.69 |
| -928 | AS568-928 | -28 | 1-3/4 | 2-1/4-12 | 2.090 ±.018 | 0.118 ±.004 | 2.326 | 53.09 ±0.46 | 3.00 ±0.10 | 59.09 |
| -932 | AS568-932 | -32 | 2 | 2-1/2-12 | 2.337 ±.018 | 0.118 ±.004 | 2.573 | 59.36 ±0.46 | 3.00 ±0.10 | 65.36 |
20 published boss sizes (AS568-901…932, with catalog gaps).
Common hydraulic ports use -904, -906, -908, -910, -912, and -916.
Shop
Hydraulic Boss O-Rings.
Common ORB ports → boss O-Ring
| ORB dash | Thread (UN/UNF) | Nom. tube | Boss O-Ring |
|---|---|---|---|
| -4 | 7/16-20 | 1/4″ | AS568-904 |
| -6 | 9/16-18 | 3/8″ | AS568-906 |
| -8 | 3/4-16 | 1/2″ | AS568-908 |
| -10 | 7/8-14 | 5/8″ | AS568-910 |
| -12 | 1-1/16-12 | 3/4″ | AS568-912 |
| -16 | 1-5/16-12 | 1″ | AS568-916 |
| -20 | 1-5/8-12 | 1-1/4″ | AS568-920 |
| -24 | 1-7/8-12 | 1-1/2″ | AS568-924 |
| -32 | 2-1/2-12 | 2″ | AS568-932 |
For materials, install notes, and 90-duro practice, see SAE J1926 ORB Boss O-Rings.
Other size charts
| Need | Chart |
|---|---|
| AS568 dash (0xx–4xx) | AS568 O-Ring Size Chart |
| Metric / ISO 3601 | Metric O-Ring Size Chart |
| JIS S/P/G/V | JIS B 2401 Size Chart |
| ORB / 900-series boss | ORB Boss Size Chart |
| Back-up rings | Backup Ring Size Chart |
| DIN 3771 | DIN 3771 Size Chart |
| Generic Metric | Generic Metric Size Chart |
| BS 4518 | BS 4518 Size Chart |
| BS 1806 | BS 1806 Size Chart |
| NF T 47-501 | NF T 47-501 Size Chart |
| SMS 1586 | SMS 1586 Size Chart |
| X-Ring | X-Ring Size Chart |
| Square Ring | Square Ring Size Chart |
| Parker 500 | Parker 500 Size Chart |
| ISO 6149 ports | ISO 6149 Size Chart |
| Search across standards | Master O-Ring Size Chart |
| Measure an unknown ring | How to Measure an O-Ring |
| Groove depth / width | Groove Charts |
Related
- Sizing overview
- Master O-Ring Size Chart
- AS568 O-Ring Size Chart
- SAE J1926 ORB Boss O-Rings
- Shore A Hardness (90 duro boss stock)
History and explanation of ORB boss seals
What a boss seal is
An O-Ring Boss (ORB) connection is a straight-thread hydraulic port. The male stud screws into a female boss. The elastomer does the sealing—usually in a machined chamfer—while the threads mainly hold the joint together.
The O-Rings for that job are the AS568 900-series sizes (AS568-901 … 932, with the
usual catalog gaps). They are boss gaskets, not the familiar 0xx–4xx face or radial dashes.
How AS568 and SAE J1926 fit together
| Document | Role |
|---|---|
| AS568 | Defines the 900-series O-Ring IDs, cords, and tolerances used as boss seals |
| SAE J1926 | Defines the inch ORB port and stud geometry (female port and male ends) |
In short: J1926 is the metal; the 9xx dash is the rubber that seals it. Older military boss cavity drawings (for example AS5202-era practice) may still appear on prints; when you have a choice, modern catalogs prefer J1926 port dimensions for tighter cavity control.
Why boss seals got their own dash family
Standard AS568 0xx–4xx sizes are built for rectangular glands (pistons, rods, face seals). A boss seal sees a different squeeze path—often a diagonal compression into a chamfer under a fitting shoulder or washer. The 900-series cords and IDs are sized for that fitting family, which is why a “close” -214 is the wrong answer for an ORB -8 port.
Naming you will hear on the floor
People use several labels for the same connection style:
- ORB / O-Ring Boss
- SAE straight thread O-Ring
- SAE J1926
- Boss seal / AS568 900-series
Those names point at one sealing idea. They are not synonyms for NPT pipe thread, JIC flare, or ORFS face seal.
How dash numbers relate to fittings
Except for the special small -901, the digits after the leading 9 track nominal tube OD in sixteenths of an inch. Example: -908 pairs with 1/2″ tube language and a -8 ORB fitting; -916 pairs with 1″ / -16.
That is why the table above lists both the boss O-Ring dash and the ORB fitting dash.
What this chart does not tell you
It will not pick compound or hardness. Hydraulic boss service usually wants a harder ring (often 90 Shore A NBR or FKM)—see the ORB guide and Shore A Hardness.
It also will not set torque. Use the fitting maker’s wet-torque chart, and leave PTFE tape off ORB threads.
Using this chart
- Identify the port or fitting dash (or measure the ring’s ID and CS).
- Match the 9xx row above.
- Confirm compound for the fluid and temperature.
- Shop Hydraulic Boss O-Rings or search from the code links in the table.
