The Fits TOTO 3 In. Flapper by Korky features an oversized sealing surface to fit large 3 In. TOTO flush valves. The exclusive longest lasting red rubber resists chlorine, bacteria, city water treatment, hard water, and well water. Authorized replacement for TOTO flapper model THU138S. Made of flexible rubber for a tight seal and easy to install. Stainless steel chain attachment.