AS568 standard size, dash -908
AS568-908 O-ring: 0.644 in ID x 0.087 in cross-section
AS568-908 is the AS568 dash 908 O-ring size. It has a 0.644 in (16.36 mm) inside diameter and a 0.087 in (2.21 mm) cross-section, which gives a 0.818 in (20.78 mm) outside diameter as a reference. AS568 controls the inside diameter and the cross-section; the outside diameter is derived.
- Inside diameter
- 0.644 in16.36 mm, +/- 0.009 in
- Cross-section
- 0.087 in2.21 mm, +/- 0.003 in
- Outside diameter
- 0.818 in20.78 mm, reference
- Series
- 9xx bossstraight-thread tube fitting seal
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Specifications
| Dimension | Value | Tolerance |
|---|---|---|
| Inside diameter (ID) | 0.644 in 16.36 mm | +/- 0.009 in |
| Cross-section (W) | 0.087 in 2.21 mm | +/- 0.003 in |
| Outside diameter (reference) | 0.818 in 20.78 mm | derived: ID + 2 x W |
| Standard | AS568 (SAE Aerospace Standard) | inch authoritative |
Millimeter values are converted. Port and groove dimensions follow the boss fitting standard on your drawing and the compound sheet.
Source for the dimensions and tolerances on this page and the nearby sizes: Parker® O-Ring Handbook ORD 5700, 2021 printing, section IX, AS568 size tables, pages 9-2 to 9-11, read 2026-09-27. Inch values are authoritative and millimeters are converted at 25.4.
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Cross-reference
Mil-spec and AMS callouts for AS568-908
AS568-908 is the dash number the military and SAE part standards below use for this same nominal size. The document sets the compound; the dash sets the nominal dimensions. When the print calls it out as a part number, such as M83461/2-908, follow that number to its own page for the document status and both units.
| Designator | Document | Compound | Status | Back-up ring |
|---|---|---|---|---|
| M83461/2-908 | MIL-P-83461/2; superseded by SAE AMS-P-83461/2, then by SAE AS83461/2 | NBR | Canceled (MIL-P-83461/2); SAE AS83461/2 adopted by DoD (2010) | see drawing |
| AS3208-08 | SAE AS3208 (AMS7276) | FKM | AS3208A stabilized (2020) | see drawing |
| MS29512-08 | MIL-P-5315 (MS29512 boss drawing); now SAE AS29512 (AMS-P-5315) | NBR | Canceled (MIL-P-5315); AS29512C current (revised 2016, reaffirmed 2021) | see drawing |
| AS9385-08 | SAE AS9385 (AMS7267) | VMQ silicone | Canceled (SAE-AS9385) | see drawing |
Document statuses are read from DLA ASSIST and SAE Mobilus (read 2026-09-24 and 2026-09-25, with SAE's current-revision records read 2026-09-27). This table carries no durometer; the document sets it.
To quote it, send the designator exactly as the print reads, with its revision and any suffix letter. Parts are supplied against the document named and quoted in the compound the print calls out.
- On MIL-P-83461/2 (30 January 1991) the boss part number takes the three-digit AS568 dash: the sheet assigns its dash numbers on the AS568 dash system, so the part number for the AS568-903 size is M83461/2-903, the sheet's own example. DLA ASSIST records the sheet as inactive for new design from 1997-12-31 (Notice 1) and canceled on 2003-10-01 (Notice 2, which refers future acquisitions to SAE AMS-P-83461/2), DoD's adoption of SAE-AMS-P-83461/2 as withdrawn on 2010-01-20, and SAE-AS83461/2 as adopted the same day and Active (idents 71937, 213940 and 277054, read 2026-10-04).
- The MS29512 Revision C sheet (1965-09-01), the DoD drawing behind the MS29512 part numbers, lists -08 at the AS568-908 nominal size, and it holds the inside-diameter tolerance tighter than AS568 above 0.500 in ID. DoD canceled the drawing on 2001-03-01, and SAE-AS29512 superseded it with the same part numbers (DLA ASSIST ident 41787, read 2026-09-27). Your drawing governs.
- The MS9385 Revision A sheet (1975-01-17), the DoD drawing behind the AS9385 part numbers, lists -08 at the AS568-908 nominal size, and it holds the inside-diameter tolerance tighter than AS568 above 0.500 in ID. DoD canceled the drawing on 1999-12-29, and SAE-AS9385 superseded it with the same part numbers (DLA ASSIST ident 37860, read 2026-09-27). SAE cancelled AS9385 in October 2020 (AS9385A is the cancellation), and DoD withdrew its adoption on 2024-02-22; the withdrawal notice says SAE superseded AS9385 with SAE-AS9386 (DLA ASSIST ident 207707 and SAE Mobilus AS9385A, read 2026-09-27). One manufacturer's aerospace cross-reference (Freudenberg, July 2024, read 2026-09-27) says AS9386 now includes the former AS9385 boss parts as -9YY. Both numbers are quoted as printed. Your drawing governs.
Compounds for an AS568-908 O-ring
| Family | Standard range | Typical media |
|---|---|---|
| Viton (FKM) | -26 C to 204 C | fuels, oils, heat |
| Buna-N (NBR) | -34 C to 100 C | mineral oils, hydraulic fluid |
| EPDM (EPDM) | -57 C to 150 C | water, steam, glycol; never petroleum oils |
| Silicone (VMQ) | -54 C to 204 C | dry heat and cold, static service |
| FFKM (FFKM) | -26 C to 320 C | aggressive chemistry and temperature beyond FKM (FFKM vs FKM) |
| HNBR (HNBR) | -32 C to 149 C | oil with heat |
| Fluorosilicone (FVMQ) | -73 C to 177 C | fuels at low temperature |
| Polyurethane (AU/EU) | -40 C to 82 C | abrasion and high pressure |
| Aflas® (FEPM) | -9 C to 232 C | steam, amines, sour gas |
| Butyl (IIR) | -59 C to 121 C | gas impermeability, brake fluid and phosphate esters; never oil |
| Polyacrylate (ACM) | -21 C to 177 C | hot transmission oil; poor at low temperature and in water |
| Ethylene-acrylic (AEM) | -40 C to 149 C | hot automotive oil |
| SBR (SBR) | -46 C to 100 C | the compound sheet governs |
| Natural rubber (NR) | -50 C to 70 C | the compound sheet governs |
| Epichlorohydrin (ECO) | -40 C to 135 C | the compound sheet governs |
The compound sheet sets the limit for a specific grade. The butyl, polyacrylate and ethylene-acrylic ranges are the handbook's section 2.2 figures (Parker ORD 5700, read 2026-09-14); the SBR and natural rubber (both dry heat) and epichlorohydrin ranges are Apple Rubber's printed standard-compound figures (Apple Rubber Seal Design Guide, read 2026-09-27). Name the compound your drawing calls out and we quote AS568-908 in it.
Viton® is a trademark of The Chemours Company; Aflas® is a trademark of AGC; Parker® is a trademark of Parker Hannifin Corporation. No affiliation or endorsement is implied.
Nearby sizes in the 9xx boss series
| Dash | ID in | ID mm | W in | W mm |
|---|---|---|---|---|
| AS568-905 | 0.414 | 10.52 | 0.072 | 1.83 |
| AS568-906 | 0.468 | 11.89 | 0.078 | 1.98 |
| AS568-907 | 0.530 | 13.46 | 0.082 | 2.08 |
| AS568-908 | 0.644 | 16.36 | 0.087 | 2.21 |
| AS568-909 | 0.706 | 17.93 | 0.097 | 2.46 |
| AS568-910 | 0.755 | 19.18 | 0.097 | 2.46 |
| AS568-911 | 0.863 | 21.92 | 0.116 | 2.95 |
Nearby sizes from the same Parker ORD 5700 section IX AS568 tables as the dimensions above.
Frequently asked
What are the dimensions of an AS568-908 O-ring?
AS568-908 has a 0.644 in (16.36 mm) inside diameter with a 0.087 in (2.21 mm) cross-section, which gives a 0.818 in (20.78 mm) outside diameter as a reference. AS568 controls the inside diameter and the cross-section; the outside diameter is derived.
What tolerance applies to AS568-908?
The inside diameter carries plus or minus 0.009 in (0.23 mm) and the cross-section plus or minus 0.003 in (0.08 mm). Both come from the AS568 table for this dash number.
Which compounds is AS568-908 available in?
The compound your drawing or specification calls out. The families below show published ranges; the compound sheet sets the limit. Send the compound and we quote the size in it.
Which mil-spec part numbers share the AS568-908 size?
M83461/2-908, AS3208-08, MS29512-08, AS9385-08 all call out the AS568-908 nominal dimensions; each document sets its own compound and hardness class. Send the designator exactly as the print reads and we quote against that document.
Orders are handled under Conquest Seal's AS9100D quality management system, whose certificate scope includes distribution.
Need AS568-908 in a specific compound or quantity?
Send the part number, the material and the quantity. A Conquest representative reads every request and replies within one business day.
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