Did the math and I was wrong to suppose the um range, the optimal thickness is more around 10-100nm depending on the material.
No this is for work, I manufacture scientific equipment for universities. Not in a big-project-expensive-stuff way, just teaching equipment at quite low prices.
This would be for a metal hall effect demonstrator, a variation of the same product I design to measure the hall effect on germanium. However, it is half as interesting as in germanium and 100 times harder to measure,