The Fluidmaster 502P21 PerforMAX Water-Saving Toilet Flapper is designed to upgrade your 2" toilet flapper. Adjustable for a customized flush and water-savings. Simply turn the dial left for more water per flush, or right for less depending on your needs. Improve flush performance and eliminate common leak and running toilet problems. Built to last, the 502 is a long lasting flapper with a 5 year warranty, and built-in Microban technology. Only Fluidmaster has toilet flappers with built-in Microban protection. Not just simply a coating, Microban is specifically built into the construction of our flappers to fight flapper breakdown and combat bacteria for a long lifespan. The Fluidmaster PerforMAX Flapper quickly replaces and upgrades your old, or corroded 2" toilet flappers. Works with 1.28, 1.6 and 3.5 GPF toilets.