O-Rings vs Gaskets: What’s the Difference?

Set of rubber gaskets

O-rings and gaskets are commonly used to create a sealed mating surface between two or more components. They are found in everything from machines and motors to plumbing fixtures and gas pipelines.

When multiple components are joined together, an O-ring or gasket may be installed at the area where they meet. Once installed, the respective component will seal the components so that they don’t leak. While both O-rings and gaskets offer a sealed mating surface, though, they aren’t necessarily the same.

What Is an O-Ring?

Also known as a packing joint, an O-ring is a type of mechanical seal consisting of a circular-shaped piece of elastomer material. They are designed to create a sealed mating surface that’s resistant to pressure. Some O-rings, in fact, can withstand pressure in excess of 5,000 pounds per square inch (PSI). Even when exposed to severe pressure, O-rings will maintain their integrity while preventing liquids, gas or air from escaping the respective components with which they are used.

Although they are available in a variety of sizes, all O-rings have the same shape. They consist of a looped piece of elastomer material with a hollow center. This circular shape allows O-rings to fit over cylindrical-shaped components, such as pipes and hoses.

What is a Gasket?

A gasket is a mechanical seal consisting of a flat piece of material. By definition, an O-ring is technically a gasket, but not all gaskets are O-rings. O-rings are made exclusively of an elastomer material, resulting in an elastic texture that’s able to stretch and revert back to its natural shape and size without breaking. Gaskets, on the other hand, can be made of any material. Some gaskets are made of an elastomer material. Others, however, are made of harder materials, such as metal. Most automotive engines, for instance, have a head metal gasket that sits between the cylinder head and the engine block.

Gaskets also come in different shapes. O-rings, on the other hand, only come in a circular shape. Many gaskets are designed in a custom shape to fit complex mating surfaces. If a mating surface has four or more components, it may require a custom-shaped gasket rather than a simple O-ring.

In Conclusion

Gaskets and O-rings are both used to create a sealed mating surface between two or more components. O-rings are simply circular-shaped gaskets consisting of an elastomer material, whereas gaskets are flat seals consisting of any material or shape.