The rotary shaft seal is constructed with a metal casing which is coved in a rubber material and can be used on any size of shaft.
The rubber covering prevents the mental casing from rusting and helps prevent damage to the housing during assembly.
The double lipped seal (TC/R23 or KC) seals against the internal media and offers an auxiliary lip which provides protection against dirt and dust.
This design is often used where space is at a premium or when a low friction application is required.