Cassette seals are designed to maximise grease or oil retention and protection against liquid or solid contaminants. These seals are provided with their own bushings in which dirt is kept out and oil/grease kept in by a multi-lip seal.

oil seal 22 32 7. This helps to prolong the life of the machinery and reduce the risk of mechanical failures.
The durometer of an oil seal is typically dependent on the material it is made with. Common oil seal materials along with their durometers are as follows: