With just one easy pull of the power pack, tramp iron falls off, ready to collect more! Zip Clean power Pack Magnetic Grids are the strongest and surest protection against tramp iron damage. Their unique design features rectangular power packs in place of conventional round tube type magnets.They produce more pulling and holding power than any other magnet made and are the ONLY magnetic grids that are 100% magnetic-including diverters. Power Pack magnets are manufactured of Ceramic and Super Strength Rare Earth materials.