Ferrite Core, YAMAY 10-Pack Snap On 5mm Ferrite Core Cord Ring Choke Bead RFI EMI Noise Suppressor Filter for Power Cord USB Cable Antenna HDMI Audio Cable Fits for cord with 5mm inner diameter Helps reduce EMI on AC power lines. Great for cutting noise on USB, Firewire, Phone, Power Cord, Coaxial, Audio, Video etc cables. Easy Structure and convenient installtion. Just clip it on and you will get clearer signal and faster data transmission. Package Content : 10 x Ferrite Cable Clips