The SMRN0655 ring neodymium magnet is made from high-performance N42 NdFeB, with Nickel coating. The dimension of this item is 1/4″ od × 1/8″ id × 1/4″ thick, magnetized diametrical, with the tolerance of ±0.004″ × ±0.004″ × ±0.004″. The weight of this super strong neodymium magnet is 0.00249375 lbs. It can pull up to 1.36 lbs steel. And the surface field is up to 5299 gausses.