Hi Vince,
I don't know, what Alex was reffering to...but, 0,1 and 0,2-0,3 mm correspond to Studer A721 (Revox B215/H1) cassette deck...amongst others, likely. And, if I reccolect correctly, his align tapes are made on a modified Revox B215.
0,1 mm should be the longitudioanal/axial "play" of...