The largest slip-joint fittings are generally 1-1/2". In the case of older toilets with separate tank and bowl connected by a standard 2" Closet Flush Elbow, 2" slip-joint fittings are needed! That is what these fittings are for, and they work very well! I primarily needed new 2" slip-joint washers, but was glad to obtain the nice new shiny scratch-free slip-joint nuts as well! :-)