According to the United States Department of Transportation and the Office of Hazardous Materials Safety, it is against regulations to ship a magnet by air that maintains a field of more than 0.00525 gauss measured at 4.5 meters (15 feet) from any surface of the package. This is to prevent the magnet from interfering with the operation of the aircraft's navigational compass. There are no federal regulations that restrict the shipping of magnetized materials by ground transportation. Please check with your commercial carrier for additional specifics.