Aluminium foil is a key material for the protection of cables, as it is a perfect barrier and highly corrosion- and heat-resistant. As a sheath for cables, aluminium foil helps to give long-term protection against moisture and other naturally occurring elements found above and below the ground. Aluminium foil also acts as an insulator against the magnetic and radio frequency emissions associated with electrical cables. In fibre-optic cable applications, the electrical conductivity of aluminium foil means that it can be used as a 'tracer' to enable testing of the integrity of cable links.