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O-Ring Size Standard

ISO 3601 Metric O-Ring Sizes & Tolerances

The international O-ring standard: ISO 3601-1 defines inside diameters, cross-sections and dimensional tolerances (Class A mirrors AS568 inch sizes; Class B is true metric), while ISO 3601-3 sets the visual quality-acceptance grades. Engineers use it to spec a size and grade with confidence; ARC molds every ISO 3601 size to your compound, hardness and grade.

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Using the ISO 3601 chart to spec your O-ring

ISO 3601 is the international O-ring size standard engineers reach for when a drawing calls out a metric O-ring by code rather than a raw dimension. Part 1 (ISO 3601-1) fixes the inside diameter, cross-section and dimensional tolerances — Class A sizes mirror the AS568 inch series, while Class B covers true metric sizes — and Part 3 (ISO 3601-3) defines the visual quality-acceptance grades (N, S and CS) for surface and molding defects. Read the chart to confirm the exact ID x CS, the tolerance class and the quality grade before you release the part, so the seal drops into your groove and passes inspection the first time.

Once you have the size and grade, ARC molds it to your spec. Twenty years of US custom rubber manufacturing, ISO 9001:2015 and IATF 16949:2016 certification, and a full range of compounds — NBR, HNBR, FKM/Viton, EPDM, silicone and more — mean you pick the material and hardness for your temperature, pressure and chemical duty, and we hold the ISO 3601 dimensions and quality grade you need. Send a size code, cross-section or drawing and our engineers confirm material, tolerance class and grade with a fast quote.

ISO 3601

American Rubber Corp is fully compliant to the dimension and tolerance standards spelled out in ISO 3601-1 Class A for all standard series O-rings and Class B for all metric series O-rings. Subsequently, American Rubber Corp defines the quality acceptance criteria of all O-rings to be in accordance with ISO 3601-3 Grade N which classifies surface imperfections and specifies maximum acceptable limits for these imperfections. This information can be viewed in PDF format here. Stricter tolerance and inspection requirements can be achieved upon customer request.

ISO 3601-1: Dimensional Tolerances

American Rubber Corp is fully compliant to the dimension and tolerance standards spelled out in ISO 3601-1 Class A for all standard series O-rings and Class B for all metric series O-rings. Subsequently, American Rubber Corp defines the quality acceptance criteria of all O-rings to be in accordance with ISO 3601-3 Grade N which classifies surface imperfections and specifies maximum acceptable limits for these imperfections. This information can be viewed in PDF format here. Stricter tolerance and inspection requirements can be achieved upon customer request.

ISO 3601-3: Quality Acceptance Criteria

ISO 3601-3 was originally developed for general-purpose O-rings, but over the years this standard has been revised and refined to include three grades (N, S, CS) of defects depending upon the application.
  • Grade N: The standard of acceptance for general-purpose O-rings.
  • Grade S: Quality requirements for optimum performance industrial applications and aerospace applications.
  • Grade CS: Special and critical sealing applications, such as certain aerospace applications and critical oxygen service applications.
Examples of surface imperfections characterized by this standard include flash, offset, parting-line projection, back rind, excessive trimming, flow marks, non-fills, and indentations.

ISO 3601 Metric O-Rings Size Chart

Issued by the International Organization for Standardization, the ISO 3601 standard contains two groups of O-Rings, Class A and Class B. Class A corresponds to the American standard AS 568B in its current format (the 900 series tube fitting O-Rings are not included). The ISO 3601-1 Size Code for these O-Rings is the same as the AS 568 dash number. Class B allows production of O-Rings in technically acceptable and economical “metric” sizes, which can then fit into metric grooves. The first digit of the Size Code indicates the cross section group (A-E), while the last four digits indicate the O-Ring inside diameter rounded to one-tenth millimeter.
For a complete listing of all metric o-ring sizes, visit our Metric O-Ring Cross Reference Table.
Global Part#ReferenceC/S (MM)I.D. (MM)C/S (Inch)I.D. (Inch)
1.80X001.8A00181.81.80.0710.071
1.80X002A00201.820.0710.079
1.80X002.24A00221.82.240.0710.088
1.80X002.5A00251.82.50.0710.098
1.80X002.8A00281.82.80.0710.11
1.80X003.15A00321.83.150.0710.124
1.80X003.55A00361.83.550.0710.14
1.80X003.75A00381.83.750.0710.148
1.80X004A00401.840.0710.157
1.80X004.5A00451.84.50.0710.177
1.80X004.87A00491.84.870.0710.192
1.80X005A00501.850.0710.197
1.80X005.15A00521.85.150.0710.203
1.80X005.3A00531.85.30.0710.209
1.80X005.6A00561.85.60.0710.22
1.80X006A00601.860.0710.236
1.80X006.3A00631.86.30.0710.248
1.80X006.7A00671.86.70.0710.264
1.80X006.9A00691.86.90.0710.272
1.80X007.1A00711.87.10.0710.28
1.80X007.5A00751.87.50.0710.295
1.80X008A00801.880.0710.315
1.80X008.5A00851.88.50.0710.335
1.80X008.75A00881.88.750.0710.344
1.80X009A00901.890.0710.354
1.80X009.5A00951.89.50.0710.374
1.80X010A01001.8100.0710.394
1.80X010.6A01061.810.60.0710.417
1.80X011.2A01121.811.20.0710.441
1.80X011.8A01181.811.80.0710.465
1.80X012.5A01251.812.50.0710.492
1.80X013.2A01321.813.20.0710.52
1.80X014A01401.8140.0710.551
1.80X015A01501.8150.0710.591
1.80X016A01601.8160.0710.63
1.80X017A01701.8170.0710.669
1.80X018A01801.8180.0710.709
1.80X019A01901.8190.0710.748
1.80X020A02001.8200.0710.787
1.80X021.2A02121.821.20.0710.835
1.80X022.4A02241.822.40.0710.882
1.80X023.6A02361.823.60.0710.929
1.80X025A02501.8250.0710.984
1.80X025.8A02581.825.80.0711.016
1.80X026.5A02651.826.50.0711.043
1.80X028A02801.8280.0711.102
1.80X030A03001.8300.0711.181
1.80X031.5A03151.831.50.0711.24
1.80X032.5A03251.832.50.0711.28
1.80X033.5A03351.833.50.0711.319
1.80X034.5A03451.834.50.0711.358
1.80X035.5A03551.835.50.0711.398
1.80X036.5A03651.836.50.0711.437
1.80X037.5A03751.837.50.0711.476
1.80X038.7A03871.838.70.0711.524
1.80X040A04001.8400.0711.575
1.80X041.2A04121.841.20.0711.622
1.80X042.5A04251.842.50.0711.673
1.80X043.7A04371.843.70.0711.72
1.80X045A04501.8450.0711.772
1.80X047.5A04751.847.50.0711.87
1.80X050A05001.8500.0711.969
1.80X053A05301.8530.0712.087
1.80X056A05601.8560.0712.205
1.80X060A06001.8600.0712.362
1.80X063A06301.8630.0712.48
1.80X067A06701.8670.0712.638
1.80X071A07101.8710.0712.795
1.80X075A07501.8750.0712.953
1.80X080A08001.8800.0713.15
1.80X085A08501.8850.0713.346
1.80X090A09001.8900.0713.543
1.80X095A09501.8950.0713.74
1.80X100A10001.81000.0713.937
1.80X106A10601.81060.0714.173
1.80X112A11201.81120.0714.409
1.80X118A11801.81180.0714.646
1.80X125Al2501.81250.0714.921
2.65X004.5B00452.654.50.1040.177
2.65X005.3B00532.655.30.1040.209
2.65X006B00602.6560.1040.236
2.65X006.9B00692.656.90.1040.272
2.65X008B00802.6580.1040.315
2.65X009B00902.6590.1040.354
2.65X009.5B00952.659.50.1040.374
2.65X010B01002.65100.1040.394
2.65X010.6B01062.6510.60.1040.417
2.65X011.2B01122.6511.20.1040.441
2.65X011.8B01182.6511.80.1040.465
2.65X012.5B01252.6512.50.1040.492
2.65X013.2B01322.6513.20.1040.52
2.65X014B01402.65140.1040.551
2.65X015B01502.65150.1040.591
2.65X016B01602.65160.1040.63
2.65X017B01702.65170.1040.669
2.65X018B01802.65180.1040.709
2.65X019B01902.65190.1040.748
2.65X020B02002.65200.1040.787
2.65X021.2B02122.6521.20.1040.835
2.65X022.4B02242.6522.40.1040.882
2.65X023.6B02362.6523.60.1040.929
2.65X025B02502.65250.1040.984
2.65X025.8B02582.6525.80.1041.016
2.65X026.5B02652.6526.50.1041.043
2.65X028B02802.65280.1041.102
2.65X030B03002.65300.1041.181
2.65X031.5B03152.6531.50.1041.24
2.65X032.5B03252.6532.50.1041.28
2.65X033.5B03352.6533.50.1041.319
2.65X034.5B03452.6534.50.1041.358
2.65X035.5B03552.6535.50.1041.398
2.65X036.5B03652.6536.50.1041.437
2.65X037.5B03752.6537.50.1041.476
2.65X038.7B03872.6538.70.1041.524
2.65X040B04002.65400.1041.575
2.65X041.2B04122.6541.20.1041.622
2.65X042.5B04252.6542.50.1041.673
2.65X043.7B04372.6543.70.1041.72
2.65X045B04502.65450.1041.772
2.65X046.2B04622.6546.20.1041.819
2.65X047.5B04752.6547.50.1041.87
2.65X048.7B04872.6548.70.1041.917
2.65X050B05002.65500.1041.969
2.65X051.5B05152.6551.50.1042.028
2.65X053B05302.65530.1042.087
2.65X054.5B05452.6554.50.1042.146
2.65X056B05602.65560.1042.205
2.65X058B05802.65580.1042.283
2.65X060B06002.65600.1042.362
2.65X061.5B06152.6561.50.1042.421
2.65X063B06302.65630.1042.48
2.65X065B06502.65650.1042.559
2.65X067B06702.65670.1042.638
2.65X069B06902.65690.1042.717
2.65X071B07102.65710.1042.795
2.65X073B07302.65730.1042.874
2.65X075B07502.65750.1042.953
2.65X080B08002.65800.1043.15
2.65X085B08502.65850.1043.346
2.65X090B09002.65900.1043.543
2.65X095B09502.65950.1043.74
2.65X100B10002.651000.1043.937
2.65X106B10602.651060.1044.173
2.65X112B11202.651120.1044.409
2.65X118B11802.651180.1044.646
2.65X125B12502.651250.1044.921
2.65X132B13202.651320.1045.197
2.65X140B14002.651400.1045.512
2.65X150B15002.651500.1045.906
2.65X160B16002.651600.1046.299
2.65X170B17002.651700.1046.693
2.65X180B18002.651800.1047.087
2.65X190B19002.651900.1047.48
2.65X200B20002.652000.1047.874
2.65X212B21202.652120.1048.346
2.65X224B22402.652240.1048.819
2.65X230B23002.652300.1049.055
2.65X236B23602.652360.1049.291
2.65X243B24302.652430.1049.567
2.65X250B25002.652500.1049.843
3.55X014C01403.55140.140.551
3.55X015C01503.55150.140.591
3.55X016C01603.55160.140.63
3.55X017C01703.55170.140.669
3.55X018C01803.55180.140.709
3.55X019C01903.55190.140.748
3.55X040C04003.55400.141.575
3.55X041.2C04123.5541.20.141.622
3.55X042.5C04253.5542.50.141.673
3.55X043.7C04373.5543.70.141.72
3.55X045C04503.55450.141.772
3.55X046.2C04623.5546.20.141.819
3.55X047.5C04753.5547.50.141.87
3.55X048.7C04873.5548.70.141.917
3.55X060C06003.55600.142.362
3.55X061.5C06153.5561.50.142.421
3.55X063C06303.55630.142.48
3.55X065C06503.55650.142.559
3.55X067C06703.55670.142.638
3.55X069C06903.55690.142.717
3.55X071C07103.55710.142.795
3.55X073C07303.55730.142.874
3.55X075C07503.55750.142.953
3.55X077.5C07753.5577.50.143.051
3.55X080C08003.55800.143.15
3.55X082.5C08253.5582.50.143.248
3.55X085C08503.55850.143.346
3.55X087.5C08753.5587.50.143.445
3.55X090C09003.55900.143.543
3.55X092.5C09253.5592.50.143.642
3.55X095C09503.55950.143.74
3.55X097.5C09753.5597.50.143.839
3.55X100C10003.551000.143.937
3.55X103C10303.551030.144.055
3.55X106C10603.551060.144.173
3.55X109C10903.551090.144.291
3.55X112C11203.551120.144.409
3.55X115C11503.551150.144.528
3.55X118C11803.551180.144.646
3.55X122C12203.551220.144.803
3.55X125C12503.551250.144.921
3.55X128C12803.551280.145.039
3.55X132C13203.551320.145.197
3.55X136C13603.551360.145.354
3.55X140C14003.551400.145.512
3.55X145C14503.551450.145.709
3.55X150C15003.551500.145.906
3.55X155C15503.551550.146.102
3.55X160C16003.551600.146.299
3.55X165C16503.551650.146.496
3.55X170C17003.551700.146.693
3.55X175C17503.551750.146.89
3.55X180C18003.551800.147.087
3.55X185C18503.551850.147.283
3.55X190C19003.551900.147.48
3.55X195C19503.551950.147.677
3.55X200C20003.552000.147.874
3.55X212C21203.552120.148.346
3.55X218C21803.552180.148.583
3.55X224C22403.552240.148.819
3.55X230C23003.552300.149.055
3.55X236C23603.552360.149.291
3.55X250C25003.552500.149.843
3.55X258C25803.552580.1410.157
3.55X265C26503.552650.1410.433
3.55X280C28003.552800.1411.024
3.55X290C29003.552900.1411.417
3.55X300C30003.553000.1411.811
3.55X307C30703.553070.1412.087
3.55X315C31503.553150.1412.402
3.55X335C33503.553350.1413.189
3.55X355C35503.553550.1413.976
3.55X020CO2003.55200.140.787
3.55X021.2CO2123.5521.20.140.835
3.55X022.4CO2243.5522.40.140.882
3.55X023.6CO2363.5523.60.140.929
3.55X025CO2503.55250.140.984
3.55X025.8CO2583.5525.80.141.016
3.55X026.5CO2653.5526.50.141.043
3.55X028CO2803.55280.141.102
3.55X030CO3003.55300.141.181
3.55X031.5CO3153.5531.50.141.24
3.55X032.5CO3253.5532.50.141.28
3.55X033.5CO3353.5533.50.141.319
3.55X034.5CO3453.5534.50.141.358
3.55X035.5CO3553.5535.50.141.398
3.55X036.5CO3653.5536.50.141.437
3.55X037.5CO3753.5537.50.141.476
3.55X038.7CO3873.5538.70.141.524
3.55X050CO5003.55500.141.969
3.55X051.5CO5153.5551.50.142.028
3.55X053CO5303.55530.142.087
3.55X054.5CO5453.5554.50.142.146
3.55X056CO5603.55560.142.205
3.55X058CO5803.55580.142.283
5.30X037.5D03755.337.50.2091.476
5.30X038.7D03875.338.70.2091.524
5.30X040D04005.3400.2091.575
5.30X041.2D04125.341.20.2091.622
5.30X042.5D04255.342.50.2091.673
5.30X043.7D04375.343.70.2091.72
5.30X045D04505.3450.2091.772
5.30X046.2D04625.346.20.2091.819
5.30X047.5D04755.347.50.2091.87
5.30X048.7D04875.348.70.2091.917
5.30X050D05005.3500.2091.969
5.30X051.5D05155.351.50.2092.028
5.30X053D05305.3530.2092.087
5.30X054.5D05455.354.50.2092.146
5.30X056D05605.3560.2092.205
5.30X058D05805.3580.2092.283
5.30X060D06005.3600.2092.362
5.30X061.5D06155.361.50.2092.421
5.30X063D06305.3630.2092.48
5.30X065D06505.3650.2092.559
5.30X067D06705.3670.2092.638
5.30X069D06905.3690.2092.717
5.30X071D07105.3710.2092.795
5.30X073D07305.3730.2092.874
5.30X075D07505.3750.2092.953
5.30X077.5D07755.377.50.2093.051
5.30X080D08005.3800.2093.15
5.30X082.5D08255.382.50.2093.248
5.30X085D08505.3850.2093.346
5.30X087.5D08755.387.50.2093.445
5.30X090D09005.3900.2093.543
5.30X092.5D09255.392.50.2093.642
5.30X095D09505.3950.2093.74
5.30X097.5D09755.397.50.2093.839
5.30X100D10005.31000.2093.937
5.30X103D10305.31030.2094.055
5.30X106D10605.31060.2094.173
5.30X109D10905.31090.2094.291
5.30X112D11205.31120.2094.409
5.30X115D11505.31150.2094.528
5.30X118D11805.31180.2094.646
5.30X122D12205.31220.2094.803
5.30X125D12505.31250.2094.921
5.30X128D12805.31280.2095.039
5.30X132D13205.31320.2095.197
5.30X136D13605.31360.2095.354
5.30X140D14005.31400.2095.512
5.30X145D14505.31450.2095.709
5.30X150D15005.31500.2095.906
5.30X155D15505.31550.2096.102
5.30X160D16005.31600.2096.299
5.30X165D16505.31650.2096.496
5.30X170D17005.31700.2096.693
5.30X175D17505.31750.2096.89
5.30X180D18005.31800.2097.087
5.30X185D18505.31850.2097.283
5.30X190D19005.31900.2097.48
5.30X195D19505.31950.2097.677
5.30X200D20005.32000.2097.874
7.00X109E109071090.2764.291
7.00X112E112071120.2764.409
7.00X115E115071150.2764.528
7.00X118E118071180.2764.646
7.00X122E122071220.2764.803
7.00X125E125071250.2764.921
7.00X128E128071280.2765.039
7.00X132E132071320.2765.197
7.00X136E136071360.2765.354
7.00X140E140071400.2765.512
7.00X145E145071450.2765.709
7.00X150E150071500.2765.906
7.00X155E155071550.2766.102
7.00X160E160071600.2766.299
7.00X165E165071650.2766.496
7.00X170E170071700.2766.693
7.00X175E175071750.2766.89
7.00X180E180071800.2767.087
7.00X185E185071850.2767.283
7.00X190E190071900.2767.48
7.00X195E195071950.2767.677
7.00X200E200072000.2767.874
7.00X206E206072060.2768.11
7.00X212E212072120.2768.346
7.00X218E218072180.2768.583
7.00X224E224072240.2768.819
7.00X230E230072300.2769.055
7.00X236E236072360.2769.291
7.00X243E243072430.2769.567
7.00X250E250072500.2769.843
7.00X258E258072580.27610.157
7.00X265E265072650.27610.433
7.00X272E272072720.27610.709
7.00X280E280072800.27611.024
7.00X290E290072900.27611.417
7.00X300E300073000.27611.811
7.00X307E307073070.27612.087
7.00X315E315073150.27612.402
7.00X325E325073250.27612.795
7.00X335E335073350.27613.189
7.00X345E345073450.27613.583
7.00X355E355073550.27613.976
7.00X365E365073650.27614.37
7.00X375E375073750.27614.764
7.00X387E387073870.27615.236
7.00X400E400074000.27615.748
7.00X412E412074120.27616.22
7.00X425E425074250.27616.732
7.00X437E437074370.27617.205
7.00X450E450074500.27617.717
7.00X462E462074620.27618.189
7.00X475E475074750.27618.701
7.00X487E487074870.27619.173
7.00X500E500075000.27619.685
7.00X515E515075150.27620.276
7.00X530E530075300.27620.866
7.00X545E545075450.27621.457
7.00X560E560075600.27622.047
7.00X580E580075800.27622.835
7.00X600E600076000.27623.622
7.00X615E615076150.27624.213
7.00X630E630076300.27624.803
7.00X650E650076500.27625.591
7.00X670E670076700.27626.378
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