I am trying to re-attach the standard trip lever that comes with the Toto Promenade. It comes with a black rubber ring I would have guessed belongs between the outside of the tank and the chrome base of the lever (to prevent the metal from scratching the tank). However, the ring has a square (rather than circular) cutout in the center, which strongly suggests it belongs on the lifting mechanism inside the tank. Protecting the inside of the tank seems odd, but cutting a square hole in a ring that belongs outside the tank seems even more unusual. If it goes inside, then I suppose is it just acting like a lock-washer, and the outside of the tank does not need protection. If it goes on the outside, then I just don't understand the shape. Does anyone know if this ring belongs inside or outside of the tank?