O-rings
Parco is a leading manufacturer of O-rings. An O-ring is a solid-rubber seal shaped like a doughnut or torus. When compressed between mating surfaces, an O-ring blocks the passage of liquids or gases. Parco O-rings are available in a wide range of standard and non-standard sizes that are suitable for nearly all sealing applications. Two dimensions describe the size of an O-ring: its inside diameter (ID) and its cross-sectional diameter (CS).
Standard O-ring Sizes
There are 369 standard sizes of O-rings with inside diameters ranging from 0.029 to 25.940 inches and cross sections ranging from 0.040 to 0.275 inch. Standard sizes are available in five popular cross-sectional diameters (0.070, 0.103, 0.139, 0.210 and 0.275 inch). Each O-ring size is identified by a "dash number." Each Parco "dash number" is the same as Aerospace Standard AS568B, Aerospace Size Standard for O-rings. Those designations are used throughout the O-ring industry. Parco offers O-rings in all 369 standard sizes and has hundreds of molds for non-standard sizes. In addition, Parco also offers all 20 sizes of boss seals used for sealing straight-thread tube fittings on a boss.
International O-ring Sizes
Standard O-ring sizes are defined by International Standard ISO 3601-1:2008: Fluid power systems—O-rings—Part 1: Inside diameters, cross-sections, tolerances and size identification code. That standard groups sizes into three classes: Class A for general industrial and aerospace applications, Class B for general industrial applications and an unlettered class for Aerospace Metric Applications. Classes A and B have three-digit Size Codes that are equivalent to the three-digit dash numbers in AS568B. There are only two differences among AS568B, Class A and Class B: Classes A and B do not address the 25 sizes of O-rings listed in AS568B as straight thread tube fitting boss gaskets, and Class B offers wider inside diameter tolerances, especially on larger sizes. ISO 3601-1:2008 also lists 360 sizes based on the former Series G Metric Aerospace sizes that were listed in the previous revision of the standard. The former Series A sizes have been discontinued. Metric cross sectional diameters differ from AS568B by less than 0.001”. Therefore, many AS568B sizes are interchangeable with a metric size. Be sure to consult ISO 3601-1:2008 for specific metric dimensions, as inside diameters may differ.
If Parco does not have a mold for a non-standard size or a particular metric size, we can make one for you.
View Parco’s O-ring Size Chart for additional information on O-ring sizes, dimensional tolerances, and cross-sections. |
Below is a list of our Popular Compounds for O-rings. If you need additional help, use Parco’s Compound Wizard to search our compound library.
Compound | Elastomer | Color | Description |
| 5601-70 | Ethylene-propylene | Black | 70-durometer ethylene propylene; general purpose; sulfur-cured; FDA-conforming. |
| 5778-70 | Ethylene-propylene | Black | 70-durometer ethylene propylene; internally lubricated; peroxide-cured; NSF-61 listed. |
| 5611-80 | Ethylene-propylene | Black | 80-durometer ethylene propylene; peroxide-cured; MIL R 3065 compliant. |
| 9005-75 | Fluorocarbon | Brown | 75-durometer fluorocarbon. |
| 9505-75 | Fluorocarbon | Brown | 75-durometer fluorocarbon; low cost; general purpose. |
| 9009-75 | Fluorocarbon | Black | 75-durometer fluorocarbon; AMS 7276 and MIL R 83248 compliant; QPL-listed. |
| 9266-75 | Fluorocarbon | Black | 75-durometer fluorocarbon; AMS 7276 and MIL R 83248 compliant; QPL-listed. |
| 9500-75 | Fluorocarbon | Black | 75-durometer fluorocarbon; low cost; general purpose. |
| 9009-90 | Fluorocarbon | Black | 90-durometer fluorocarbon; AMS 7259 and MIL R 83248 compliant; QPL-listed. |
| 9021-95 | Fluorocarbon | Black | 95-durometer fluorocarbon. |
| 1902-60 | Fluorosilicone | Black | 60-durometer fluorosilicone; AMS R 25988, AMS 3325, and MIL R 25988 compliant. |
| 1933-70 | Fluorosilicone | Black | 70-durometer fluorosilicone; AMS R 25988 and MIL R 25988 compliant. |
| 2269-70 | HNBR | Black | 70-durometer HNBR; peroxide-cured. |
| 2269-90 | HNBR | Black | 90-durometer HNBR; peroxide-cured. |
| 3110-70 | Neoprene | Black | 70-durometer neoprene; general purpose; AMS 3209 and MIL PRF 1149 compliant. |
| 4457-65 | Nitrile | Black | 65-durometer nitrile; AMS P 5315 compliant. |
| 0228-70 | Nitrile | Black | 70-durometer nitrile; FDA-conforming; UL-listed; SAE J120 R1 compliant. |
| 4200-70 | Nitrile | Black | 70-durometer nitrile; FDA-conforming; AMS 3215 compliant; UL-listed. |
| 4900-70 | Nitrile | Black | 70-durometer nitrile; low cost; general purpose. |
| 4067-70 | Nitrile | Black | 70-durometer nitrile; MIL P 25732 compliant; QPL-listed. |
| 4456-70 | Nitrile | Black | 70-durometer nitrile; MIL G 21569, MIL P 82745, and SAE J120 R1compliant |
| 4367-70 | Nitrile | Black | 70-durometer nitrile; peroxide-cured; AMS P 83461 and MIL P 83461 compliant; QPL-listed. |
| 0483-80 | Nitrile | Black | 80-durometer nitrile; sulfur-cured. |
| 2067-90 | Nitrile | Black | 90-durometer nitrile. |
| 4900-90 | Nitrile | Black | 90-durometer nitrile; low cost; general purpose. |
| 4177-90 | Nitrile | Black | 90-durometer nitrile; sulfur-cured. |
| 4058-90 | Nitrile | Black | 90-durometer nitrile; sulfur-cured; MIL R 3065 compliant. |
| 1200-70 | Silicone | Brick Red | 70-durometer silicone; general purpose; AMS 3304 compliant. |
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