Cardas RCA Caps (RCA C) fit over unused female RCA connectors in your system to eliminate EMI and RF noise absorption. Unlike traditional shorting plugs, these caps do not short the inputs (many pre amps do not like having their inputs shorted). Another difference is Cardas RCA Caps completely cover the RCA input with a solid shield of nickel and brass to prevent both EMI and RFI from entering the chassis through the RCA dielectric. This is a more elegant and probably more effective solution than either shorting plugs or wrapping the plug in aluminum foil. Our caps also protect the RCA from dust and corrosion.