These VERY powerful magnets are made of an alloy of the rare earth element Neodymium along with Iron and Boron. This is the most powerful permanent magnet alloy known.
These magnets are plated in gold to seal the sensitive alloy from moisture. They are cubes 12 millimeters on a side.
These magnets work great as the top magnet in the Magnet in Mid-air project because of their strength. We supply them in 4 packs because they are also ideal for levitating pyrolytic graphite.
CAUTION: Neodymium magnets are so powerful that they will break if allowed to jump together. Work with them on a steel surface to prevent jumping.