What is an O-Ring? (Buy Now)

An o-ring is a round, mechanical gasket designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface. O-Rings are one of the most common types of seals because they are inexpensive, reliable and have simple mounting requirements. Since they are known as one of the most important elements of machine design, O-rings may be used in static applications, where little range of motion is required. O-Rings may be used in dynamic applications, like rotating pump shafts and hydraulic cylinder positions, also (o-ring chart).


O-Ring Compounds

We offer many different o-ring compounds for a variety of applications. Visit our Compounds page to see a list of all our standard compounds and their properties.

O-Ring Material

Material matters. Due to this, selecting an o-ring material for a specific application is dependent on many criteria, including what is being sealed, temperature range, pressure, dynamic or static service, desired service life, installation considerations, tolerances, and many more. General purpose compounds are used broadly, however, utilizing the exact compound consistently is equally as important. At Sterling Seal and Supply, Inc, you can be assured that all our general-purpose O-rings meet the standards stated in our spec sheets. We do not mix compounds even for general purpose O-rings. To learn which o-ring materials will work best in your application. Material Selection Guide and Chemical Compatibility Table.


Determining durometer is not hard. The hardness of rubber compounds is measured by the Shore A durometer, the higher the durometer, the harder the compound. In addition, softer compounds stretch easier and seal better on rough surfaces. Harder compounds offer greater abrasion resistance and resistance to extrusion. To learn more about o-ring durometer, click here.


There is more to O-rings than meets the eye. Specific color standards are routinely used to help visually identify the type of o-ring installed for certain industries. Because of this, we stock O-rings in the most common colors, materials, and compounds.

Shelf Life

Shelf life for O-rings can vary anywhere from three years to unlimited, depending on elastomer type.

Metric O-Rings

Sterling Seal & Supply, Inc. offers a large selection of metric o-ring sizes in various compounds. A “metric o-ring” simply means that the size of the o-ring is defined in millimeters.

Custom Molded O-Rings

Beyond our huge inventory of more than 50 million O-rings in all standard materials and sizes, if you are looking for a custom size o-ring for any cross-sections larger than the AS568 400 Series (.275” CS) and/or an ID larger than the largest ID for that series, we’re your go-to provider.

Product Inquiry

View our AS568 Size Chart for a full listing of all sizes and dimensions.