Stupid question: Is it I.D. or O.D. ?
 

Basically, I can't remember how this works. My system uses 1/2 inch fittings. Does this mean my Maze2, DTek core and Eheim use 1/2 inch OD, while my 1/2 inch tubing from DangerDen is 1/2inch ID?

Or are they all the same size and the tube simply streches over the fittings?

I ask because I'm getting ready to replace my entire system with compression fittings and a nice new double-tap bleed line and I need to make sure all the fittings I get will be able to work with each other and my current hardware.

Thanks.

When devices in your watercooling system are rated for 1/2", that means you use 1/2" ID hose.. Doesn't matter if the OD is 5/8" or 3/4", just as long as the ID is 1/2".. :)

Well thats what I thought, but I measured the DangerDen barbs and they are a little less then 1/2 inch. Compareing them to a piece of 1/2 inch tube (its says 1/2 ID on the side, so I'm sure about it) made it clear that they were a little smaller. They're much bigger then a 3/8, but I wasn't sure and didn't want to risk getting $30 worth of the wrong size fittings.

Thanks.