Foil Shield

A type of cable shield composed of a thin layer of mylar-backed aluminum foil in contact with a copper drain wire used to terminate it. The foil shield/drain wire combination is very cheap, but it severely limits flexibility and indeed breaks down under repeated flexing. It’s the only commonly available shield type that offers true 100% coverage, however, this advantage is somewhat compromised by its high transfer impedance (aluminum being a poorer conductor of electricity than copper), especially at low frequencies. It does allow for very small cables and is often a preferred shield in permanent installations where space is much more of a concern than durability.