Great for cutting noise on USB, Firewire, Phone, Cord, Coaxial, Audio, Video etc cables Just snap it on and you will get clearer signal and faster data transmissionThese snap-on ferrite cores are superb at reducing high frequency interference caused by home appliances and electronics. Can be installed on any electrically-noisy home device, for example telephones, televisions, speaker cables, radios, touch lamps and lights, even audio equipment and appliancesInner Diameter:3.5mmColor:Blackmaterial: metalOverall Size:3.5mm:Approx.2.5 x 1.3cm/ 0.98 x 0.5"Package Contents:10 x EMI RFI Noise Ferrite Core FilterOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.