About O-Rings

An O-ring, which is also known as a packing or a toric joint, has circular-looped shape and is referenced as a torus.  It is designed to be seated in a groove and then compressed during it’s use to help seal two working surfaces.

Seal & Design Inc. can fulfill all your molded needs whether they be transfer, injection (LIM) or compression molded from any type of elastomer. Seal & Design can also produce rubber-to-metal bonded products as well as extruded sponge rubber or homogeneous profiles.

Products can be supplied in all types of elastomers. There are hundreds of various formulations designed around customer requirements.

Learn more about molded compounds on the Elastomeric Compounds Page.

Standard Sizes (AS568B)

The standard sizes used by o-ring manufacturers in the United States are defined by Aerospace Standard AS568B, Aerospace Size Standard for O-rings. That document, published by the Society of Automotive Engineers (SAE), lists the sizes of O-rings in six series or groups in both inches and millimeters. The first five series are based on cross-sectional diameter. The sixth series includes 20 sizes for boss seals. The standard sizes are also used for most military specifications.

Cross-sectional diameters range from 0.040 to 0.275 inch. Inside diameters range from 0.029 to 25.940 inches. There are 369 standard sizes.

Metric Sizes

Standard metric sizes for O-rings are defined by International Standard ISO 3601-1:2002: Fluid power systems O-rings Part 1: Inside diameters, cross-sections, tolerances and size identification code. That standard groups metric sizes into two series, G and A. The G series is used for general purpose applications and includes a wide range of inside diameters. The A series is used for aerospace applications where tighter tolerances are recommended. The G series has 445 sizes and the the A series has 383 sizes.

Currently, ISO sizes do not use a dash numbering system like the Aerospace Standard. ISO cross-sectional diameters differ from the Aerospace Standard by less than 0.001 inch. Therefore, many AS568B sizes are interchangeable with an ISO size. Be sure to consult ISO 3601-1 for specific dimensions, as inside diameters may differ.

O-Ring Sizes: Standard & Metric Sizes

There are two main o-ring sizing types: standard and metric. Standard was developed for use in the United States, while the international community uses metric sizes. The metric sizes are further broken down by region, notably Europe and Japan.

Learn more about O-Ring sizes with the links below.

Seal & Design has all these sizes and more. We can provide virtually any required size.

Technical Information

Seal & Design is a world-class seal & gasket manufacturer and a name you can trust for gasket, seal and o-ring solutions.  Technical sealing has been defined by DIN Standards as follows:

• Static Seal – The sealing action created between two mating surfaces with no leakage of liquid or minimal diffusion of gas.
• Dynamic Seal – The mating surfaces have relative movement with minimal leakage of liquid (useful to protect the sealing efficiency, acting as lubricant)

The simple geometry is the main characteristic of an O-Ring which, in conjunction with proper elastomer selection results in a low cost, easy to use and efficient sealing system. Elastomeric materials, when compressed, react like a high viscosity fluid which transmits applied stress in every direction; consequently, the O-Ring serves as a barrier, blocking the leak paths between the sealing surfaces.

O-Rings offer several advantages over other sealing systems: simplicity of construction, standardized seal dimensions, wide selection of materials, suitability for both static and dynamic applications, standard dimensioning of glands, low cost due to high volume manufacturing.

Sealing is always achieved through a positive compression or squeezing action, resulting in a deformation of the O-Ring cross-section. The most important sealing characteristic of an O-Ring is its resistance to compression set or residual deformation.

Standard Sizes (AS568B)

We stock a full line of o-rings in a wide variety of sizes, shapes, and compounds. Popular offerings include: Viton® O-Rings, Buna-N O-Rings, Silicone O-Rings, Chemraz® O-Rings, EPDM O-Rings, PTFE O-Rings, Neoprene O-Rings, Metric O-Rings, Back-Up RingsX-Rings, Square Rings, Spliced O-Rings. We also make custom o-rings for specific applications.

O-Ring Offerings


O-Ring Special Features Available

  • Special packaging, barcoding, and private labelling
  • Silicone coating
  • Dipped external o-ring lube designed for ease of installation
  • Moly/Graphite Lube
  • Molybdenum dasulfide external o-ring lube
  • Parafin filled – internal
  • Wax based o-ring lube – moderate lubridity
  • Silicone lube – internal
  • O-rings or special molded parts can be produced in any color

Why Choose Seal & Design for Your O-Rings?

Seal & Design has years of experience manufacturing and distributing sealing products of all kinds from standard O-ring sizes to specialized products. Our O-rings come in a wide range of sizes and materials so you can find the right product for your project no matter the application. 

We also have great customer service so you can feel confident choosing the right products for your business or project. When you’re unsure which O-ring is right for you, we’re there to help. Give us a call and we’ll be happy to walk you through all of the options we have available to you.

Which O-Ring Material Is Right for Me?

When you’re choosing an O-ring for your project, it’s important to keep in mind the different factors that will affect the O-ring material. These factors include:

  • The application of the O-ring
  • The pressure the O-ring will be under
  • The temperature the O-ring will be subjected to
  • The size of the fastener
  • The medium being sealed

Each of these factors will have an impact on how the O-ring performs. Not all O-ring materials are effective in every environment, and what works during one application may not work in another. 

Silicone rubber O-rings are the most popular material choice because they’re capable of performing in a wide range of temperatures without melting or hardening. However, silicone rubber does have its limits. The average temperature range for silicone rubber O-rings is between -62 and 204 degrees Celsius. Other O-ring materials such as Nitrile and fluorosilicone are versatile as well, but have shorter temperature ranges.

Not sure which O-ring material is the right fit? We’ve got you covered. Contact Seal & Design today to get a professional opinion on the right O-rings for you. We’ll be more than happy to answer any questions you may have.


Millions of o-rings in all standard AS568-B sizes.


A wide variety of gasketing products - fabricated in dozens of materials in hundreds of formulations


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O-Ring and gasketing material with strong chemical resistance properties

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