To understand length contraction better, would an precise instrument where width, height and length must be exact equal for working when standing still in frame A, still working in its rest frame B at a higher speed in frame A with length contraction ? With other words, is length contraction just real in the meaning of time depended but not real in another physical explanation (e.g. on atom level) ? Or is it general to say when two persons moving (same size), both sees the other length contracted, both can be descriped as an physical explanation (e.g. on atom level) in their own rest frames (will be experienced) ... so you see just all happened in your own frame and all is just real for you only inside your frame ?