The SMBN0638 block neodymium magnet is made from high-performance N52 NdFeB, with Nickel coating. The dimension of this item is 4″ × 2″ × 1″ thick, magnetized through thickness, with the tolerance of ±0.004″ × ±0.004″ × ±0.004″. The weight of this super strong neodymium magnet is 2.16875 lbs. It can pull up to 536.2 lbs steel. And the surface field is up to 4174 gausses.