. . . "but not limited to, vulcanized rubber or one of the polychloroprene-based synthetic rubbers (for example, neoprene), which can easily conform to the shape and size of any drain or siphon, thereby forming a water-tight seal.The stopper 8 may be configured as a bellows or other shape that is capable of deforming both the vertical and the horizontal directions with the application of a compressive fo" .