The aerators mainly come in two sizes. The regular size usually measures 15/16″ for males or 55/64″ for the female’s faucet. In contrast, the junior aerator measures 13/16″ for the Male and 3 /4″ for the female faucet. To find a suitably fit aerator for your faucet, you will need to measure it or do the coin trick, so if your faucet is the size of a nickel, you will need a regular size aerator. But if the faucet is rough of the size of a dime, you will need a junior size aerator to fit in perfectly.