EPCOS - TDK Corporation Ferrite Rings
Ferrite rings, which some people refer to as ferrite beads or chokes, suppress high-frequency noise that sometimes develops in electronic circuits. These rings are passive electrical components, and they typically come coated in epoxy or uncoated. In either case, ferrite rings prevent electromagnetic interference between devices in both directions. It's common to see them on external cabling. In fact, it's ferrite rings that you sometimes see near the end of a plug or USB cable. In some cases, these rings are used internally on circuit boards around pins or conductors. When used internally, ferrite rings are small. Regardless of where they're used, the goal is always to block unwanted noise.
Epocs is part of TDK Corporation, which is among the world leaders in manufacturing electronic components. It makes a number of passive components, so its production line isn't limited to ferrite rings. Some of the other products that Epocs manufactures are inductors, film capacitors and aluminum electrolytic capacitors.