5 Pcs Amidon Iron Powder Toroidal Core T-30-2 Tangda T30 Iron powder cores T30-2 OD*ID*HT 7.8*3.8*3.3 mm 4.3nH/N2 10uo Iron dust core Ferrite Toroid Core Coating Red gray 5 pieces Micrometals Amidon T30-2 Iron Powder Toroidal Core T-30-2 Toroid Microm