This highly efficient little aerator can be used anywhere to lower your water use to only 1.0 GPM at 80 psi. It is chrome plated over solid brass with a life expectancy of 10 years. Less than 1" in diameter, its dual thread construction is 15/16" for outside threads and 55/64" for inside threads. This aerator is certified by the California Energy Commisson and meets or exceeds ASME standards. It provides an even spray and huge water savings and is one of the best affordable aerators on the market. Approximately 1/2" in diameter.