Fangrui Product Details 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.