The SMRN0657 ring neodymium magnet is made from high-performance N42 NdFeB, with Nickel coating. The dimension of this item is 3/8″ od × 3/32″ id × 3/8″ thick, magnetized diametrical, with the tolerance of ±0.004″ × ±0.004″ × ±0.004″. The weight of this super strong neodymium magnet is 0.0105 lbs. It can pull up to 5.35 lbs steel. And the surface field is up to 6590 gausses.