> DOM is not necessarily seamless, just dimensionally more precise.
And part of that is concentricity of the inner and outer diameters. For
regular structural and or plumbing pipe, there's no real requirement (or
need) for the wall to be uniformly thick, as long as it is at least as
thick as the minimum required. I've seen some standard black iron pipe
where the inside was distinctly oval and not centered.
If you've got an application where you are nesting or telescoping the
tubes, pipe can be a surprise.
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