② The material of the paired floating seal ring must be the same material (usually alloy cast iron), and the hardness of the sealing end face is 60～72HRC. If the material and hardness are inconsistent, the oil seal will fail due to uneven wear.

③ The flatness of the sealing end face of the floating seal ring
The sealing of the floating oil seal is ensured by the rigid contact of the sealing end surface of the floating seal ring. Because the two floating seal rings rotate relative to each other, elastic and plastic deformation cannot be used to fill the unevenness of the sealing end surface; the sealing end surface has high flatness accuracy and can be on the end surface. A thin and complete oil film is formed, so that the sealing end faces of the two floating seal rings are in a suspended state, reducing wear.