I got a box of these rare earth cell phone thingies - you put a metal plate on the cell phone, and the attach the magnet to the dash of the car, and mount the phone there - well, I work in a building with metal walls, so I brought a bunch of these in to hold stuff to the wall - I swear, when I snap one to the wall, I have to use a screwdriver to pry it off!!!! They are the most powerful magnets I have ever had, and I have played around a lot. Weird thing, there is a copper placed disk on one side of the magnets, and there is ABSOLUTELY no magnetic properties getting through that disk!