The Fluidmaster Duo Flush System allows quick conversion of existing toilet into a dual flush toilet. Duo Flush uses less water by offering 2 different flush settings, 1 for liquids and 1 for solids. With Duo Flush technology you save up to 45% more water without sacrificing flush performance. Duo Flush replaces the toilet flapper which eliminates the potential for leaks in the future. The Duo Flush System comes with PerforMAX fill valve to maximize toilet performance and water savings. The PerforMAX fill valve is the quietest and most powerful fill valve sold.