A. These "will fit" flappers are unique in that a variety of inserts are included to allow you to control how much water flushes from your toilet each time it is used. When you flush the toilet, the trip lever lifts the chain on the flapper to allow the water in the tank to flow into the bowl through the flush valve. The bottom cone-like part of the flapper holds air in it. Once lifted, the flapper floats until the water in the tank recedes, when the flapper lands back on the opening of the flush valve. These inserts allow you to control the amount of water that flows into the flapper cone while it is open or floating in the water, thus controlling how fast the flapper seals the flush valve opening.