This is a 3 mm diameter sphere made of magnetized neodymium. He is considered one of the metals with higher ferromagnetic property.
I bought a package with 216 of these spheres, that form a puzzle quite interesting. You can put them in an ellipse as shown below, where not used all walks.
Or you can attach them two at a time and shape this strange effect worm.
You can also put them four-four in this format, Although it is kind of hard because any false move and all the marbles get together.
There are all the 216, least some that I missed, placed in the format four-four.
If you get the wrong balls way they approach and saw this larger sphere.
I found out that you can put the balls in a Helix forming a cylinder, look how it looks:
The same format with a larger cylinder:
But beware of the stress, If you irritate will do only this format even:
They also cling on any ferromagnetic metal, as this on a real coin. Look how the pellets are small if compared to the currency.
I have several of these magnets, are interesting to study magnetic effects and puzzle for fun. Those interested the balls can be purchased in stores DealExtreme FocalPrice and: