I am re-installing an undersink water filteration system. The supply line for the filter is a 1/4" flexible plastic tubing.
Also, I don't want the filteration constantly supplied with water. We should be able to turn the water supply on and off to the filteration system.
The current cold water valve and supply line is 3/8".
What sort of valves and fittings do I need for this project. I know there will be some sort of T-connector involved and there will be some kind of valve to turn the supply on/off to the filteration system.

Any help you can provide with the links to the plumbing supplies on homedepot/lowes website will be much appreciated.

Thank you.

[www.ebay.com]
If you have 1/2 inch copper lines before you supply stops you can cut the tubing and add one of these. If there isn't room, you can remove the stop, but leave the nut and ferrule and put this in place of the stop. You will need a short piece of copper (4 inches or so) and use one of the new nuts and ferrule and add the stop back in.

Perhaps the easiest would be to use a 3/8 x 3/8 add-a-tee adapter with a 1/4 fitting for your filter:
[www.lowes.com]

The easiest way is to reconnect the unit the way it was, then cut the 1/4" supply tube and use a 1/4" "push on John Guess" quarter turn ball valve in the line.

Fixitangel , thanks for the advise, but I need a valve to control the flow to the filteration system. One of the outlets from the T should be connected to the valve and the valve in turn be connected to the 1/4" flexible tubing to the water filter.

Thank you.