Where the heck would you get 1/4" walled tubing? I've never heard of it. If you are going by the dimensions of the tube, .750" OD and .500" ID you only have 1/8" walls. Divide that number by 2 and that's how much wall you have on each "side" of the tube, if you were looking at a cross section. I don't even know it that makes any sense. I'm not usually up this early since I work nights, and I haven't had any coffee yet!