The valve is marked with an in and out on one side to help guide you in its orientation. There are a few systems out there that are plumbed differently but you will still be able to use this valve if you follow the proper in and out flow connections.

This can also be used as a replacement for valves with Jaco thread style fittings, simply cut off the tubing before the Jaco nut and push into the JG style push in fitting on the valve. (*You may need a short piece of tubing if this makes the tube too short or if your orientation is different, a longer tube will overcome any configuration issues.