The plastic plug-in unit wipes off the dirt on the surface of the sphere during opening and closing. which has a good protective effect on the sealing ring. Plug-in unit prevents the ball and valve seat from scratching due to dimension deviation during sphere installation. When there is a need for grease injection, a sealing ring is formed by the sealing grease between the elastomer and the plug-in unit. Emergency sealing can be achieved with only a small amount of grease.