Leather oil seals are commonly used for parts that are exposed to dirt and poor lubrication. The major advantage of this material is that it can function in cases where synthetic rubber cannot function. They are used for shafts that have rough surfaces that are more than what rubber seals can handle. This is because they are pre-lubricated and have the capacity to absorb liquids.

The metal case is the exterior (or frame) of the oil seal, the principal function of which is to give rigidity and strength to the seal. The material of the case must be selected depending on the environment where the seals are to be used. Often the metal case is covered by the same rubber material used in the sealing element, which also helps seal the exterior of the oil seal in the housing bore. Common case material types are: