This male to female device is a handy little device so it's easy to connect 1/4inch tubing to your mains water supply. This then makes it easy to send water to your filter device, RO water system or you can use this to connect mains water to your carbonation keg lid. Most people will have under sink water supplies and various other water supplies in the house have a 1/2inch male thread. This adaptor is male to female so if you just undo your supply valve then screw this adaptor in then you can run a 1/4in tube out the side of this valve.