Another way is: draw a circle, rotate them ,pull them to tube, then union, after it use the shell tool, select both of 4 ends, set the wallthickness.
Later you can set wallthickness one by one if you need, tap inside the tube
Doing the sketch and go to offset edge to get thickness of tube .
Then drag the hi lighted part to make the first tube, then hi light both the sketch and the tube and duplicate both pieces to make the second tube or create a new sketch with new dimensions line up tubes. Then use the center part of the sketches to remove the center of tubes .