Unlike traditional molded rubber scupper flappers that can deform over time, thermoplastic elastomer flappers by T-H Marine stand up to UV light and retain their shape.Scupper flappers act as a one-way valve that allows water to flow out, but not backflow in. For the valve to function, it is important that the flapper make a positive seal. Unfortunately, exposure to UV light can cause traditional rubber flappers to curl and not seal. The remedy is to replace old, curled rubber flappers with thermoplastic elastomer flappers by T-H Marine. These flappers stand up UV-light and retain their shape—which means that water will flow out of the scupper, but not backflow in.Key FeaturesThermoplastic elastomer material stands up to UV lightKit contains 2 each of: 1 5/8" flappers, 1 7/8" flappers, and 2 1/4" flappers, plus all necessary keepers and fasteners