Best for older toilets, 3.5 GPF or more (before 1994). The Fluidmaster® 501 Universal Chlorine-Resistant Toilet Flapper is designed to be a longer lasting and high quality flapper replacement, to fit most 2” flush valves. Built tough to last in any water condition, with chlorine-resistant materials and built-in Microban®. 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. The solid frame ensures a secure seal, by resisting bending, or twisting during flushing, so you never have to jiggle the toilet handle again. Replace your leaky, or faulty flapper now, with Fluidmaster®’s 501 Solid Frame Universal Flapper.