Static

Static seals exist where there is no relative motion between the mating surfaces being sealed. Static seals are easier to design because they can handle wider tolerances, rougher surface finishes and higher pressure limits.

Dynamic

Dynamic seals exist where there is relative motion between the mating surfaces being sealed. In most instances, the dimensional variations inherent in dynamic seals make them more difficult to design and more expensive to construct than static seals. Nevertheless, dynamic O-ring seals are indispensable to a wide variety of applications.