Proprietary Chlorazone II rubber is 2 times stronger than other Toilet Flappers-- Red rubber resists chlorine, bacteria, city water treatment, hard water, and well water. Fits most 2 inch flush valves, including American Standard, Kohler, TOTO and more! The most universal 2 Inch Toilet Flapper-- Adjusts to fit all tank sizes: 1.28, 1.6, 3.5 and 5 gallon per flush toilets. Adjusts to match original toilet settings and eliminates water waste by decreasing the amount of water flushed Adjusts to match original toilet settings and eliminates water waste by decreasing the amount of water flushed Made in the USA