These iron filings are encased in a plastic bubble, used to observe the effects of invisible magnetic fields. It is supplied in a set of 10 discs. Each disc measures 8.5cm in diameter. Iron filings are very small pieces of iron that look like a powder. Iron is a ferromagnetic material, which means that each particle turns into a tiny little bar magnets. The north pole of each particle attracts the south pole of the particle next to it. Each particle behaves in the same way, creating a chain of filings parallel to the direction of the magnetic field. Iron filings are a great resource in the science classroom when used in combination with a bar magnet (not included and sold separately). The patterns of the iron filings are mesmerizing, and you will see that your students are fascinated by the magnetic fields. The iron filings even look like spikes when they form a magnetic field!