Strong magnets, conventionally refers to rare earth magnetic materials.mainly NdFeB material
Ordinary magnets, in general, are ferrite or other materials.
In fact, the powerful magnets compared with ordinary magnets, which is characterized by large field, the fold is about 4 times. Another feature is the high gradient.
The gradient represents the change of the magnetic field per unit length. The surface field is infinitely long. For example, the magnetic field intensity decreases faster and the gradient is higher. On the other hand, the magnetic field of the powerful magnet is more affected by the distance change.
The terminology is that the magnet of the powerful magnet (N52 Strong Neodymium Cyllinder Magnets)is smaller. So in the distance under the ordinary magnet to provide the suction will be higher than the powerful magnet.
30CM For a single magnet, whether it is strong or ordinary, are unable to induce enough suction.
Of course enough of the block arrangement can achieve this effect.