Vacuum breakers are a safety device required by some municipalities to hook your sinks into the public water supply. It prevents in the worse case scenario chemicals in your bowl being sucked back into the public water supply causing contamination. Some places require it and some places do not., check your local building codes. A vacuum breaker can usually be installed by a plumber even if it was not bought originally, but you will need to have your model number. Including the following parts: Connecting hose, fastening bolt and wing nut/mounting bar, brass hex nuts and pipe nipples, hose receiver cap, and vacuum breaker and vacuum breaker rubber gasket.