The SMSN0739 SPHERE neodymium magnet is made from high performance N42 NdFeB, with Nickel coating. The dimension of this item is 1/4″ diameter, with tolerance of ±0.004″. The weight of this super strong neodymium magnet is 0.0021875 lbs. It can pull up to 1.63 lbs steel. And the surface field is up to 8815 gauss.