Neodymium magnets are the strongest type of permanent magnet commercially available. And we added two! This water tight box with twin magnets is great for holding and protecting your GPS Tracker. Its inside dimensions (3.2x1.5x1.8 inches) will hold the best trackers. (View Images) Used by law enforcement and private detectives, it is surely going to work for your application. Works Great as a key holder box or anything you can think of.

Waterproof Twin Magnet Case – Strongest Magnets Commercially Available (NdFeB) Magnets. Inside dimensions 3.2 x 1.5 x 1.8 inches. Used by law enforcement and private detectives. Extremely strong case – Attach to any flat metal surface – Magnets will hold at fast speeds and bad weather. Not compatible with the Optimus 3.0. Only the Optimus 2.0.