The SMBN0404 neodymium block magnet is made from high performance N42 NdFeB, with Nickel coating. The dimension of this item is 5/16″ × 5/16″ × 5/16″ thick, magnetized through thickness, with tolerance of ±0.004″ × ±0.004″ × ±0.004″. The weight of this super strong neodymium magnet is 0.00825 lbs. It can pull up to 6.7 lbs steel. And the surface field is up to 5754 gauss.