This is a ferrite ring, not a magnet. It has no magnetism. Iron powder cores are generally stored near the signal. It has the characteristics of isolating eddy current, low permeability and restraining interference. Widely used in power , current sensors, , inductors, chokes, ballasts, voltage regulators, welding , broadband , filters and so on. You receive 17 pieces of iron powder core magnetic rings, which can meet your needs. Name:iron powder core magnetic ring Quantity:17pcs Coating:epoxy resin Weight:about 510g Colour:As Shown Material:Ferroferric oxide Size:Outer diameter:26.9mm, Inner diameter: 14.5mm, Height: 11.1mm Package Contents: 17 * Iron powder core magnetic ring Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.