Amazon.com: Fielect 10Pcs Toroid Core Ferrite Choke Iron Powder Inductor Ferrite Ring 24.1x39.9x14.5mm,Yellow and White : Office Products
uxcell Toroid Core, Ferrite Chokes Ring Iron Powder Inductor Ferrite Rings, Yellow White 13pcs, 8.2 x 15.5 x 6.2mm: Amazon.com: Industrial & Scientific