The fits TOTO G-Max 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 G-Max flapper model THU138S. This type of toilet flapper is made of flexible rubber for a tight seal and easy to install.