Buy with Confidence: With Monoprice's Lifetime Warranty on all Cables, you can rest assured we stand behind our products and our customers. Ferrite Cores are small magnetic blocks wrapped around the end of a cable They are use d to suppress EMI/RFI electronic noise on the cable by absorbing the unwanted high frequencies and dissipating them as very low-level heat This is the simplest and cheapest form of electronic noise reduction and is most effective on small gauge cabling which is inherently more susceptible to electronic noise interference than thicker cables