We have John Guest Ball Valves, in both the 1/4" and 3/8" and they come in white polypropylene. This valve connects your reverse osmosis system, as a shutoff valve. They'll stop the flow of water with a twist. These valves are not to be used with anything other than water systems.
John Guest valves have push-fit technology that allows for easy set up and connection. The push-fittings help give you quick disconnection without the need for tools. These valves are rated for water usage only, not for gas or other applications.