The center conductor is surrounded by plastic insulation, which helps filter out extraneous interference.

In addition the plastic insulation was a type which bio degrades with time and heat.

Precipitation can carry away the heat, so the ground is shielded with 6 m skirts of plastic insulation.

These applications are being replaced by plastic insulation.

Many body cords are made with clear plastic insulation so that any corrosion of the copper wire can be seen more easily.

The table below shows various data including both the resistance of the various wire gauges and the allowable current (ampacity) based on plastic insulation.

It was about two inches thick, covered in gray plastic insulation.

In cold climates, the mixture may also include jelly cable (plastic insulation from copper phone wire).

There was also an XLP series which used a hard plastic insulation, but was otherwise the same.

Some hobbyists use fine sandpaper to wear away the plastic insulation from the wires.