needle valve

Yes, but depending on how big the valve is, you might not want to go down to 10-32.

Edit - That's for in terms of mounting it. If you want to run it un-line, no issues at all. What valve are you looking at?

Yep. No worries on size. You can go from 1/4 to 1/2 to 1/16 if you wanted. You can find a 1/4 to 1/8 reducer at any hardware store, but you'll probably want to put out a WTB in the Swap n Shop if you need any 10-32 fittings (it's "10-32", not "10/32". No big deal, but it's not a size reference, and a theoretical 10/32 NPT would be bigger than 1/4 NPT, while in reality it's a heck of a lot smaller).

The deal with bigger pipe sizes is that you can deliver a larger volume per minute. (Hence a fire hose is 10x bigger than a garden hose!)

However, with CO2 the flow rate is almost undetectable and the tiniest of lines can easily deliver what you need. Unless you've got a monster tank packed to the rim with plants, you can go with the smallest fittings available and still have capacity to spare.

In searching for needle valves from a list here in the forums, I found a couple with 1/4 fnpt ends. I wasn't sure, but figured it would work because of the short distance to reduce. Didn't want to complicate or compromise pressure relationships - newbie to co2.

Snuffy