The 502 flapper is the gold standard of flappers. Not only is it our longest lasting flapper, but it also comes packed with features that ensure you're getting the best flush every time. One of the unique features of this flapper is the ability to adjust how much water is flushed. Simply turn the dial left for more water and right for less water flushed, helping save water and improve flushes. The 502 PerforMAX® Flapper is suitable for 3.5, 1.6 and 1.28 gal per flush toilets. Only Fluidmaster has toilet flappers with built-in Microban® protection. Not just simply a coating, Microban® is specially built into the construction of our flappers to fight flapper breakdown and combat bacteria.