This is an oval ring type Joint totally enclosed in a nitrile rubber coating. the ring type Joint material is usually soft iron or low carbon steel. advantage of this type of gasket:
Used in pressure testing to minimise damage to
flanges.
Rubber contact points provide additional seals while
protecting the flange surfaces.
Provides increased assurance against corrosion, which
can occur between conventional ring type Joints
and the engaged surfaces of the groove.