The 504 Flapper is built to last in any water condition with its chlorine-resistant properties. Featuring a flexible design, the 504 flapper offers the versatility of fitting both flush valves with or without mounting ears. This flapper fits most 2 in brass and plastic flush valves and is suitable for 3.5 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.