Widely used in power , current sensors, , inductors, chokes, ballasts, voltage regulators, welding , broadband , filters and so on. 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. You receive 17 pieces of iron powder core magnetic rings, which can meet your needs., Weight: 1.15522225288 Pounds, Manufacturer: Jaywool