Question PPI of Magnetic sheeting?

[2B]

why is the 20mil mag magnetized with a stronger PPI than the 30mil mag?
20 mil is magnetized to 16 poles per inch, & 30 mil is magnetized to 12 poles per inch

but yet the 20mil is not recommended for vehicle application.....

 

[bannertime]

I believe that states how it was magnetized. I also believe that a 30mil at 12ppi has more holding power than a 20mil at 16ppi.

Here's an interesting list that shows the difference. Doesn't give any math on how to figure it out.