The standard design is a simple smooth ring [ER01]. Insert rings are often equipped with a Kammprofile serrated profile on the sealing surfaces in order to improve the sealing properties [ER10]. A very practical solution is to use insert rings which are serrated on both sides and are covered with graphite foil. These insert rings are like a Kammprofile serrated gasket and the two additional non-metallic gaskets which are usually required for standard insert rings are not needed.
