The Harwil Q-16 Flow Switch is commonly used in chiller, heat pump, boiler feed and heat exchange applications as a quality replacement for any 1-inch paddle type flow switch. The Q-16 is shipped with all the stainless steel paddles needed to fit 1-inch to 8-inch pipe and is able to handle flow rates as low as 4 gpm and up to 500 gpm. Harwil paddles are heavy-duty and very strong.