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.

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.