Also known as X-rings or Quad Ring® seals, four-lobed seals double the number of sealing surfaces found on traditional O-rings. Used primarily in dynamic applications, lobed seals require less squeeze than O-rings and thus generate less friction.

Thanks to their unique design, lobed seals also provide improved sealability and are more resistant to the twisting stresses that can lead to spiral failure. Be aware, however, that lobed seals are more expensive than O-rings. Figure 139 illustrates the cross-section of a four-lobed seal.