This valve installs under the sink on the cold water line to install 1/4" tubing to an RO/DI system.

Simply unscrew the hose that runs from the cold water line, install this fitting and reconnect the hose. Then install the 1/4" tubing into the Speed Fit fitting.  The blue handle allows you to stop the feed to the RO system when filters need to be changed, or when you go out of town.