I saw some reviews about how these things are crazy strong and there is absolutely no lie in that. I had managed to pry one free from the bunch and was just seeing how well it picked up on other metal objects. As I was putting it back, I kept the plastic ring between it and the others and the thing still managed to pinch my fingers.
The other thing I've noticed while testing them out is that with metal objects, they will snap to anything metal but as in terms of actual 'holding' power, they could handle holding a small 3lb weight and do so off the ground (It was a weighted jump rope handle for context). Anything larger than that, don't expect it to hold on to, at least not by itself. A stack of 15 could hold a 10lb dumb bell off the ground with ease.
NOW, as for hanging onto things, the smooth metal design is a big fault here. I a pair of scissors on one disk and with a gentle flick of my wrist, shook the scissors off (don't try that at home unless you're crazy like me.)
Just ask why you need these magnets. If you want them on your fridge, these are too strong. If you want these holding tools, they can do that so long as the tools aren't too heavy. If you need them for something crazy like I do (Costuming) then....well use your best judgement based on what this review and others have