Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Very Strong Magnets, Very Brittle Exterior

These magnets are incredibly strong. I've placed all four of them in a row & used them as a stud finder -- they are drawn to nails in drywall like fleas to a dog.If you allow these magnets to slam together, you may end up with surface cracks and/or chips on some of them.