I thnk the previous reviewer was reviewing the wrong product. These magnets are very strong. I've used them on heavier glass objects -- about 4 to 5 oz in weight. These are a great value when in comparison to the neodymium magnets - which are more powerful, but most smaller heavier items don't need that powerful of magnet.
These magnets are terrible. They have virtually no strength and are so flimsy. If you push on the surface with your nail, it actually leaves a dent. Don't waste your money.