a standard 2x4 is actually 1.5 inches by 3.5 inches(I checked)
16 times 3.5 equals 56 inches.
However if the crates were built in Libya with local supplies I don't have a clue what size the "2x4" is
"2 X 4" is an "english" system concept. Anyy folks familiar with standars lumber sizes in the metric world? The ratio length to width is about dead on.
In the photo, the Libyan tubes appear to be wider in the middle than at the ends (not perfectly cylindrical). That may be from packing material shading parts of the tubes. For my width, I took the tubes at the widest part