As magnets go, these are the best I've used. BEWARE, though! I used them in my office and soon after started having MAJOR issues with the hard drive on my laptop. The magnets were on a board on the wall, not directly next to the computer, but apparently close enough (12" back and 12" up), so use caution if you plan to use them in your office.I would NEVER allow my children to play with them. They are super strong & powerful, and like others have mentioned, if a child happened to swallow one or more, it could cause major problems.