The chrome brass aerator with dual thread from Master Plumber is an end piece which is fixed to the orifice of the faucet to reduce its water consumption by limiting the water outflow. The 15/16" male end fits with American Standard, Delex etc. As for the 55/64" female end, it fits with Waltec, Emco etc. Water flows at 5,7 litres per minute. this aerator is made in the United States and has a O.E.M. quality.