“RARE EARTH” MAGNETS are super strong to hold your tins to any metal surface. Also called neodymium magnets.
Usually you will only need to use one magnet in a tin. No iron smell or bits of magnet in your tins. These will not rust. Handle with care. These can fly together and pinch you or crash together and break apart. That is why we only sell them with the plastic spacers for easier and safer separating.
You are buying a single magnet or multiples separated by plastic spacers for your convenience in getting them apart.
Also consider PUTTY for applications where there is not a metal surface to attach your hide containers.