O-rings in every AS568 size and ISO 3601 metric
Conquest Seal is an O-ring supplier and distributor: we stock every AS568 size, and we quote metric sizes and anything else in the compound your drawing calls for. An O-ring is a rubber ring that seals by being squeezed in a groove, and it is sized by its inside diameter and cross-section. SAE AS568 lists 369 inch sizes by dash number, most of them in five cross-sections from 0.070 in to 0.275 in, and ISO 3601-1 lists the metric sizes. Each size page names the compounds it is held in, and every order ships with a certificate of conformance. Send the dash number or the size, the compound and the quantity, and a Conquest representative quotes it.
Datasheet
The five AS568 cross-sections
| Series | Dash range | W in | W mm | W tol in | Sizes |
|---|---|---|---|---|---|
| 0xx, below the cord | -001 to -003 | 0.040 to 0.060 | 1.02 to 1.52 | +/- 0.003 | 3 |
| 0xx | -004 to -050 | 0.070 | 1.78 | +/- 0.003 | 47 |
| 1xx | -102 to -178 | 0.103 | 2.62 | +/- 0.003 | 77 |
| 2xx | -201 to -284 | 0.139 | 3.53 | +/- 0.004 | 84 |
| 3xx | -309 to -395 | 0.210 | 5.33 | +/- 0.005 | 87 |
| 4xx | -425 to -475 | 0.275 | 6.99 | +/- 0.006 | 51 |
| 9xx boss | -901 to -932 | varies | varies | varies | 20 |
-001, -002 and -003 sit below the 1.78 mm cord at 1.02, 1.27 and 1.52 mm and have no ISO 3601 metric counterpart. 349 general-purpose sizes plus 20 boss sizes. ISO 3601-1 lists the inch sizes under the same dash numbers and the metric sizes under their own codes, such as C0250.
- Size standards
- AS568 dash -001 to -475, plus metric sizes to ISO 3601
- Cross sections
- 0.070, 0.103, 0.139, 0.210 and 0.275 in (dash series 0xx to 4xx)
- Inside diameter
- 0.029 in to 25.94 in across the AS568 range
- Compound families
- FFKM, FKM (Viton®), FVMQ, VMQ, HNBR, EPDM, NBR (Buna-N), AEM (ethylene acrylic), AU/EU (polyurethane)
- Hardness
- set by the compound; each compound sheet states its Shore A hardness
- Service temperature
- -73 C to 320 C by family on the Parker® ranges (Parker O-Ring Handbook ORD 5700, section 2.2, read 2026-09-14); FFKM -26 C to 320 C (ORD 5700 page 7-2, read 2026-09-25); named grades on file reach 327 C (Kalrez® 7075) and -42 C (Kalrez 0040), each on its maker's sheet
Compounds
Compound families and their service ranges
| Family | ASTM D1418 | Standard range | Special grades | Note |
|---|---|---|---|---|
| Viton | FKM | -26 C to 204 C | to -46 C, to 232 C time-limited (about 3,000 hours) | fuels, oils and heat; low-temperature grades to -46 C |
| Buna-N | NBR | -34 C to 100 C | to -57 C, to 121 C | mineral oils and hydraulic fluid; 121 C short term |
| EPDM | EPDM | -57 C to 150 C | to 204 C | water, steam and glycol; never petroleum oil |
| Silicone | VMQ | -54 C to 204 C | to -115 C, to 260 C | dry heat and cold; static service |
| FFKM | FFKM | -26 C to 320 C | to -42 C, to 327 C | named grades on file reach 327 C (Kalrez 7075) and -42 C (Kalrez 0040), each on its maker's sheet |
| HNBR | HNBR | -32 C to 149 C | none listed | oil with heat |
| Fluorosilicone | FVMQ | -73 C to 177 C | none listed | fuels and oils at low temperature |
| Polyurethane | AU/EU | -40 C to 82 C | none listed | abrasion and high pressure; never hot water |
| Aflas® | FEPM | -9 C to 232 C | none listed | steam, amines and sour gas; poor at low temperature |
| Butyl | IIR | -59 C to 121 C | none listed | gas impermeability, brake fluid and phosphate esters; never oil |
| Polyacrylate | ACM | -21 C to 177 C | none listed | hot transmission oil; poor at low temperature and in water |
| Ethylene-acrylic | AEM | -40 C to 149 C | to 163 C | hot automotive oil |
| SBR | SBR | -46 C to 100 C | none listed | the compound sheet governs |
| Natural rubber | NR | -50 C to 70 C | none listed | the compound sheet governs |
| Epichlorohydrin | ECO | -40 C to 135 C | none listed | the compound sheet governs |
| PTFE | PTFE | no range on file | none listed | Quoted against the compound sheet; no handbook range is published here on purpose. |
Ranges are the handbook family figures, not a guarantee for a specific compound. The SBR range is the conservative bound of Apple Rubber's and ERIKS's printed figures (dry heat), and the natural rubber (dry heat) and epichlorohydrin ranges are Apple Rubber's printed standard-compound figures, the only maker's figures on file (read 2026-09-27). Name the compound or specification your print calls out and we quote the size in it.
Source for the Kalrez 7075 and Kalrez 0040 figures: Kalrez Perfluoroelastomer Parts in Chemical Process Industry, Product Selector Guide KZE-A40126, Qnity Electronics (formerly DuPont), November 2022 (read 2026-09-14).
Source for the Viton 232 C figure: The Chemours Company, Viton Fluoroelastomers Selection Guide C-11021 (9/19), page 1, which gives it as a time-limited service limit of about 3,000 hours at 232 C (read 2026-09-27).
Sizes
Every AS568 dash number, with its own page
We stock every AS568 size; each size page carries its own stock line, and a stocking program holds the sizes your line uses on our shelf against a blanket order.
0xx series: -004 to -050 at 0.070 in (1.78 mm) cross-section; -001 to -003 at 0.040 to 0.060 in-001 to -050, 50 sizes
1xx series, 0.103 in (2.62 mm) cross-section-102 to -178, 77 sizes
- -102
- -103
- -104
- -105
- -106
- -107
- -108
- -109
- -110
- -111
- -112
- -113
- -114
- -115
- -116
- -117
- -118
- -119
- -120
- -121
- -122
- -123
- -124
- -125
- -126
- -127
- -128
- -129
- -130
- -131
- -132
- -133
- -134
- -135
- -136
- -137
- -138
- -139
- -140
- -141
- -142
- -143
- -144
- -145
- -146
- -147
- -148
- -149
- -150
- -151
- -152
- -153
- -154
- -155
- -156
- -157
- -158
- -159
- -160
- -161
- -162
- -163
- -164
- -165
- -166
- -167
- -168
- -169
- -170
- -171
- -172
- -173
- -174
- -175
- -176
- -177
- -178
2xx series, 0.139 in (3.53 mm) cross-section-201 to -284, 84 sizes
- -201
- -202
- -203
- -204
- -205
- -206
- -207
- -208
- -209
- -210
- -211
- -212
- -213
- -214
- -215
- -216
- -217
- -218
- -219
- -220
- -221
- -222
- -223
- -224
- -225
- -226
- -227
- -228
- -229
- -230
- -231
- -232
- -233
- -234
- -235
- -236
- -237
- -238
- -239
- -240
- -241
- -242
- -243
- -244
- -245
- -246
- -247
- -248
- -249
- -250
- -251
- -252
- -253
- -254
- -255
- -256
- -257
- -258
- -259
- -260
- -261
- -262
- -263
- -264
- -265
- -266
- -267
- -268
- -269
- -270
- -271
- -272
- -273
- -274
- -275
- -276
- -277
- -278
- -279
- -280
- -281
- -282
- -283
- -284
3xx series, 0.210 in (5.33 mm) cross-section-309 to -395, 87 sizes
- -309
- -310
- -311
- -312
- -313
- -314
- -315
- -316
- -317
- -318
- -319
- -320
- -321
- -322
- -323
- -324
- -325
- -326
- -327
- -328
- -329
- -330
- -331
- -332
- -333
- -334
- -335
- -336
- -337
- -338
- -339
- -340
- -341
- -342
- -343
- -344
- -345
- -346
- -347
- -348
- -349
- -350
- -351
- -352
- -353
- -354
- -355
- -356
- -357
- -358
- -359
- -360
- -361
- -362
- -363
- -364
- -365
- -366
- -367
- -368
- -369
- -370
- -371
- -372
- -373
- -374
- -375
- -376
- -377
- -378
- -379
- -380
- -381
- -382
- -383
- -384
- -385
- -386
- -387
- -388
- -389
- -390
- -391
- -392
- -393
- -394
- -395
4xx series, 0.275 in (6.99 mm) cross-section-425 to -475, 51 sizes
Specifications
Military and SAE documents supplied against
The part families below come from manufacturers qualified to the document named; the certificate names the manufacturer and the current revision. Conquest Seal is a distributor and is not itself listed on any qualified products list.
Orders are handled under Conquest Seal's AS9100D quality management system, whose certificate scope includes distribution. The certificate, CONQ-001, is on the certificate page, and what ships with each part is on the quality and certifications page.
Aerospace O-rings are ordered to the specification on the print, and the aerospace page covers callouts to canceled documents and the paperwork that ships with the part.
| Document | Part families | Material | Status | Superseded by |
|---|---|---|---|---|
| SAE-AS83248/1 | AS83248/1-xxx | FKM | Reaffirmed; current revision AS83248/1A (2021-11-08), the reaffirmation date; last revised October 2016; DoD-adopted 2025-11-03, Active in ASSIST | |
| SAE-AS83248/2 | AS83248/2-xxx | FKM | Reaffirmed; current revision AS83248/2A (2021-11-09), the reaffirmation date; last revised October 2016; DoD-adopted 2025-11-03, Active in ASSIST | |
| SAE-AMS7276 | AS3208-xxx, AS3209-xxx, AS83248/1-xxx, M83248/1-xxx (legacy) | FKM | Current revision AMS7276J (2020-05-18); DoD-adopted 2023-01-17, Active in ASSIST | |
| SAE-AMS7259 | AS3581-xxx, M83248/2-xxx (legacy) | FKM | DoD-adopted 2017-08-17, Active in ASSIST | |
| SAE-AMS-P-83461 (AMSP83461) | M83461/1-xxx | NBR | Current revision AMSP83461 (1998-04-01), the original issue, no later revision; DoD-adopted 2003-10-01, Active in ASSIST | |
| SAE-AS83461/1 | AS83461/1-xxx, M83461/1-xxx (legacy callout) | NBR | Reaffirmed; current revision AS83461/1C (2021-11-08), the reaffirmation date; last revised October 2016; DoD-adopted 2010-01-20, Active in ASSIST | |
| MIL-P-25732 / MIL-PRF-25732 | MS28775-xxx | NBR | Inactive; inactive for new design since MIL-P-25732C Notice 1 (1989-11-15); latest issue Revision E (2024-03-08) | |
| SAE-AMS-P-5315 (AMSP5315) | AS29512-xxx, AS29513-xxx | NBR | Current revision AMSP5315C (2022-08-05) | |
| SAE-AMS7270 | AS3569-xxx | NBR | Current revision AMS7270M (2022-03-09) | |
| SAE-AMS7271 | AS3578-xxx | NBR | Reaffirmed; current revision AMS7271K (2025-10-22), the reaffirmation date; last revised December 2019 | |
| SAE-AMS7272 | AS3551-xxx | NBR | Current revision AMS7272G (2013-04-12) | |
| SAE-AMS7274 | AS3570-xxx | NBR | Current revision AMS7274K (2020-07-08) | |
| MIL-DTL-25988 / MIL-R-25988 | M25988/1-xxx, M25988/2-xxx, M25988/3-xxx, M25988/4-xxx | FVMQ | Inactive (Revision D Notice 1, 2025-06-11); the M25988 slash sheets are Active | |
| SAE-AMS-R-25988 (AMSR25988) | M25988/1-xxx, M25988/2-xxx, M25988/3-xxx, M25988/4-xxx | FVMQ | Current revision AMSR25988B (2023-06-27) | |
| SAE-AMS3325 | M25988/3-xxx (legacy cross-reference) | FVMQ | Current revision AMS3325H (2024-09-11) | |
| SAE-AMS3304 | AS3582-xxx | VMQ | Current revision AMS3304J (2019-04-05) | |
| SAE-AMS7267 | AS9386-xxx, AS9385-9yy | VMQ | Current revision AMS7267H (2021-05-19) | |
| SAE-AS28775 | AS28775-xxx, MS28775-xxx (legacy callout) | NBR | Reaffirmed 2025-02-08; current revision AS28775A (revised December 2008); DoD-adopted 2000-09-29, Active in ASSIST | |
| SAE-AS28778 | AS28778-yy, MS28778-yy (legacy callout) | NBR (boss gasket; usually supplied at 90) | Reaffirmed; current revision AS28778C (2021-11-08), the reaffirmation date; last revised October 2016; DoD-adopted 2001-03-01, Active in ASSIST | |
| SAE-AS29513 | AS29513-xxx, MS29513-xxx (legacy callout) | NBR | Reaffirmed; current revision AS29513C (2021-11-09), the reaffirmation date; last revised October 2016 | |
| SAE-AS29512 | AS29512-xxx, MS29512-xxx (legacy callout) | NBR | Reaffirmed; current revision AS29512C (2021-11-09), the reaffirmation date; last revised October 2016 | |
| SAE-AS9386 | AS9386-xxx, MS9386-xxx (legacy callout) | VMQ (AMS7267) | Revised; current revision AS9386B (2021-07-07) | |
| SAE-AS3084 | AS3084-xxx | FKM (via AMS7280) | Stabilized; current revision AS3084A (2012-06-06); DoD-adopted 2025-12-05, Active in ASSIST | |
| SAE-AS3085 | AS3085-xxx | FKM (via AMS7280) | Stabilized; current revision AS3085A (2012-06-06); DoD-adopted 2025-12-05, Active in ASSIST | |
| SAE-AS3208 | AS3208-xxx | FKM (via AMS7276) | Stabilized; current revision AS3208A (2020-05-12) | |
| SAE-AS3209 | AS3209-xxx | FKM (via AMS7276) | Stabilized; current revision AS3209C (2021-08-03) | |
| SAE-AS3551 | AS3551-xxx | NBR (via AMS7272) | Revised; current revision AS3551A (2020-10-09) | |
| SAE-AS3569 | AS3569-xxx | NBR (via AMS7270) | Revised; current revision AS3569A (2021-08-09) | |
| SAE-AS3570 | AS3570-xxx | NBR (via AMS7274) | Reaffirmed; current revision AS3570A (2025-07-17), the reaffirmation date; last revised January 2020 | |
| SAE-AS3578 | AS3578-xxx | NBR (via AMS7271) | Reaffirmed; current revision AS3578 (2018-08-23), no later revision | |
| SAE-AS3581 | AS3581-xxx | FKM (via AMS7259) | Stabilized; current revision AS3581A (2020-05-12) | |
| SAE-AS3582 | AS3582-xxx | VMQ (via AMS3304) | Reaffirmed; current revision AS3582 (2018-08-23), no later revision | |
| SAE-AS568 | AS568-xxx dash numbers | n/a (dimensional standard) | Reaffirmed; current revision AS568F (2026-01-29), the reaffirmation date; last revised March 2020 | |
| SAE-AS8791 | MS28774-xxx, MS28782-xx, MS27595-xxx | PTFE (back-up ring) | Reaffirmed; current revision AS8791D (2025-07-16), the reaffirmation date; last revised January 2020 | |
| MIL-DTL-25988/1 | M25988/1-xxx | FVMQ (fluorosilicone) | Active; Revision B Notice 1 (Validation), 2026-04-21 | |
| MIL-DTL-25988/2 | M25988/2-xxx | FVMQ (fluorosilicone) | Active; Revision A Notice 1 (Validation), 2026-04-21 | |
| MIL-DTL-25988/3 | M25988/3-xxx | FVMQ (fluorosilicone) | Active; Revision A Notice 1 (Validation), 2026-04-21 | |
| MIL-DTL-25988/4 | M25988/4-xxx | FVMQ (fluorosilicone) | Active; Revision A Notice 1 (Validation), 2026-04-21 |
Related O-ring products
Beyond the round AS568 O-ring
Larger and non-standard sizes: any O-ring beyond the AS568 and ISO 3601 lists is supplied to order as a spliced and vulcanized O-ring in the compound families made as cord; that page covers the two splice methods, which materials can be spliced and what to send.
Frequently asked
How do I read an AS568 dash number?
The first digit gives the cross section and the last two digits place the inside diameter within that series: 0xx is a 0.070 in section, 1xx is 0.103 in, 2xx is 0.139 in, 3xx is 0.210 in and 4xx is 0.275 in. Dash -001 to -003 are three small sections below the 0xx cord, and the 9xx series are boss gaskets for straight-thread tube ports. The number is a catalog lookup, not a formula, so use the size chart or the size page for the actual dimensions.
What tolerances does an AS568 O-ring carry?
The tolerance grows with the size. A -214 is 0.984 in inside diameter plus or minus 0.010 in with a 0.139 in cross section plus or minus 0.004 in, while a -395 at 25.94 in inside diameter carries plus or minus 0.12 in on the diameter and plus or minus 0.005 in on the section. Each size page on this site lists both tolerances for that dash number.
Can a metric O-ring replace an AS568 size?
Sometimes. The ISO 3601 metric list uses five cords, 1.8, 2.65, 3.55, 5.3 and 7.0 mm, that sit inside the AS568 cross-section tolerance bands, so the sections interchange; the inside diameters do not always line up. A -214 at 24.99 mm inside diameter sits 0.01 mm under the metric C0250, while a -006 at 2.9 mm is 0.1 mm off its nearest metric size and needs a gland check. Send both callouts and the groove dimensions and we quote the size that fits.
What does a military part number like MS28775 or M83248 on my print mean?
Those are O-ring part families tied to a material specification. MS28775 (now AS28775) is a nitrile ring to MIL-PRF-25732 for MIL-H-5606 hydraulic fluid; M83248/1 is a fluorocarbon ring to AMS7276 and M83248/2 a fluorocarbon ring to AMS7259; M25988 is a fluorosilicone ring to AMS-R-25988. The parts come from manufacturers qualified to those documents, and the manufacturer's certificate ships with every specification part.
What surface finish does the O-ring groove need?
The ERIKS O-ring Technical Handbook (chapter 12, read 2026-09-24) puts the static groove floor and top at 32 microinch Ra for liquids and 16 microinch Ra for vacuum and gases, with the groove sides at 63 microinch Ra. The Trelleborg O-Rings and Back-up Rings catalog (June 2024, read 2026-09-24) holds the mating surface of a static seal to 60 microinch Ra and the static groove flanks and diameter to 630 microinch Rt. For a dynamic seal Trelleborg holds the rod or bore to 16 microinch Ra, ground free of any spiral lead, and ERIKS asks for 8 to 16 RMS on the rubbing surface. The number alone is not the whole requirement: the lay of the finish should run with the ring, not across it.
Related guides
Viton is a trademark of The Chemours Company; Kalrez is a trademark of Qnity Electronics; Aflas is a trademark of AGC; Parker is a trademark of Parker Hannifin Corporation. Trelleborg and ERIKS are named as the publishers of documents this page cites. No affiliation or endorsement is implied.
Send the dash number, the compound and the quantity
We stock every AS568 size; any size is quoted in the compound your print calls out. A Conquest representative replies.
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