When installed, the thin side is inward and the back is outward.
Instructions for use: Tear off the foam layer around the original silicone ring with pliers, and pull the silicone ring down with pliers.
Shape the new silicone ring into a ''C'' shape and insert it into the foam layer. If there is a small hole, use the end of a small screwdriver to push it in.
Fasten the round edge to the groove of the silicone ring, and after loosening the pliers, use the pliers to wrap around the inner side of the silicone ring forcefully, and the silicone ring is replaced.