The O-ring is the most common type of fluid seal. An O-ring's simple design lends itself to a multitude of sealing uses, including static, reciprocal, oscillating, and dynamic applications at low speed and pressure. In elevated operating pressure environments, addition of a backup ring will greatly increase the extrusion resistance of an O-ring.

　　The most basic shape of an O-ring is a simple circular sealing torus, usually made from an elastomeric material. Beyond the standard O-ring, All Seals can supply more advanced sealing designs such as Quad Rings, which are specially designed for low pressure sealing. All Seals also offers O-rings in advanced materials such as Viton, Viton Extreme, and Teflon.