Toroidal cores are passive electronic components consisting of a circular ring or donut-shaped magnetic core of ferromagnetic ferrite around which wire is wound.SpecificationColor: BlackMaterial: Nickel Zinc FerriteSquareness rate: 10Bs: 400TBr: 150mTTc: 120°Cρ: 4.9g/cm3μi: 650-1000Outer Diameter: 17.5mm/0.69 inch, 18mm/0.71 inch, 20mm/0.79 inch, 22.5mm/0.89 inch, 25mm/0.98 inchInner Diameter: 9.5mm/0.37 inch, 10mm/0.39 inch, 10mm/0.39 inch, 13.8mm/0.54 inch, 15mm/0.59 inchThickness: 12.7mm/0.5 inch, 10mm/0.39 inch, 10mm/0.39 inch, 10mm/0.39 inch, 12mm/0.47 inchPacking List: 20 x Toroids (4 Pieces For Each Size)AdvantageFerrite cores are dense, homogeneous ceramic structures made by mixing iron oxide (NiZnFe2O4) with oxides or carbonates of nickel, zinc. Have very high permeability and low losses, can work at high frequencies.
eBay