This is our primary collection of metal testing magnets.  Which one is right for you depends on the application and how portable your test magnet needs to be. Larger test magnets can help find smaller amounts of ferrous content, or allow you to work faster. The trade off, however, is you lose portability and have to watch your work space carefully to insure no accidental attraction to ferrous objects occurs, and that fragile items and electronics are clear of the space.