Review on Permanent Magnets Building Scientific Magnets by David Golden

Bought 20. Received today. I return. YES, they are very durable. SO strong that they cannot be taken apart for use. There's a nice plastic O-ring between them, but it's not strong enough to pull them apart. When I finally spread them enough to grab the edge, it snapped back into the stack, taking my fingertip damn near with it - THIS IS A STICK for a while and will probably be turning blue under the nail tomorrow. My husband tried to pull them apart, he caught his finger between them and left a bloody blister! On the second try, the magnet breaks into 3 pieces. These things are VERY DANGEROUS! I don't recommend them at all. Unless you want to throw a bunch of it at someone. You are heavy!