Radial Oil Seals consist of a single lip bonded to a metal support with a garter spring. There are many different variations of the Radial Oil Seal, both with and without an integral dust excluding lip. These dust lips can be positioned either within the seal width or beyond the seal base. A successful Radial Oil Seal runs with a thin film of fluid under the sealing lip. The film acts as a lubricant and allows a meniscus to form on the other side of the sealing lip. Radial Oil Seals can also include hydrodynamic aids, which create positive sealing by returning any oil leaking back into the system. For pressures above the recommended 0.05 MPa (7.3 psi) a metallic support heel can be used.