Specification:

Name: Strong Countesunk Magnets
Material: Rare earth ndfeb
Using environment: the normal temperature, never demagnetization.

Features:
Rare super fuction: if two pieces of super magnets stick together,
a strong man is unable to use that force perpendicular to make it separate.
We should be very careful, because the magnets
  will own adsorbed together, could pinch your fingers.
There may be damaged due to collision magnet itself
  (or knocked knocked corner cracks) when magnets each other.

Note:
Magnetic force is very strong. Be carefully of cliping your hand.
You can make particle experiments like a small magnetic  separation.
Magnet away from items that easily magnetized such as floppy disks,
credit cards, computer monitors, watches, cell phones, medical equipment and so on.
Magnets should stay away from the pacemaker.
Larger sized magnet should be added plastic or cardboard shims
between each piece to ensure that the magnet can easily be separated.