Iron powder cores are generally stored near the signal. It has the characteristics of isolating eddy current, low permeability and restraining interference. This is a ferrite ring, not a magnet. It has no magnetism. Widely used in power , current sensors, , inductors, chokes, ballasts, voltage regulators, welding , broadband , filters and so on. You receive 34 pieces of iron powder core magnetic rings, which can meet your needs., Weight: 2.31044450576 Pounds, Manufacturer: Ynusgeyx