The MAG HUB is magnetized for easy detection and galvanized coating to resist corrosion. It has a large center point and looks like a standard survey marker.Not made to be driven in concrete or asphalt. They are packaged in 30 lb. boxes. The 4″ Mag Hubs have approximately 885  per box. The 6″ Mag Hubs have approximately 362 per box. The 8″ Mag Hubs have 272 per box.