Ferrite beads are one of the simplest and least expensive types of interference filters They filter out the high frequency noise in the circuit by dissipating it as heat. This item is a 10 mm long x 6 mm diameter core with 6 holes. It is wound with 2-1/2 turns of # 24 wire. The core resembles the Ferroxcube WBC design. We have large quantities of this item- call us for a quote on high volume. New, old stock