Parco is your convenient source for quality O-rings. We make all 369 standard sizes, hundreds of special sizes, and O-ring kits. We also manufacture standard and custom metric sizes. Parco offers O-rings that meet virtually every military and industrial specification. With more than 100 million O-rings in stock, Parco maintains one of the largest inventories in North America.
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. 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.
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.
|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.|
|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.|
|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; 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 and MIL P 82745 compliant|
|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.|
|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.|