When you order 5 spheres, you'll receive the K-19-C packaged with spacers in such a plastic tube.
Note: only the large sphere (K-19-C) on top is magnetic. The other 8 are simple, non-magnetic, steel spheres that are magnetised through the one magnetic sphere.
2 sphere magnets K-19-C attract each other without a problem through my forearm. Admittedly, I am only an average office-based guy and don't have construction worker arms, but still....
Somewhere in the midst of these steel spheres, there is one K-19-C.
Through a hand without a problem.